Explore topic-wise InterviewSolutions in .

This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

14051.

A body of mass 0.2kg is moving with a velocity 4m/s to bring it to rest in 10min the work done is

Answer»

M = 0.2 kg

u = 4 m/s

t = 10 min = 10 x 60 sec = 600 sec

We know

a = \(\frac{v-u}t\) = \(\frac{0-4}{600}\) = 0.006 m/s2

Then

F = ma

F = 0.2 x 0.006

F = 0.0012 N

S = ut + \(\frac12\)at2

S = 4 x 600 + \(\frac12\) x \(\frac{0.006}{1000}\times600\times600\)

S = 2400 + 180

S = 2580 m

Work done

W = F. 5

W = 0.0012 x 2580

W = 3.096 j

14052.

A body starts revolving from rest in a circular path of radius 2 m with tangential acceleration a `=2tm//s^(2)`. If its total acceleration at t=2 sec. is `nsqrt(5) m//s^(2)`, then the value of n is:

Answer» `v=t^(2)`
t=2
`a=sqrt((a_(c))^(2)+(a_(t))^(2))`
`rArrsqrt(((v^(2))/(R))^(2)+a_(t^(2)))`
`rArrsqrt((8)^(2)+(4)^(2))rArr4sqrt(5)`
14053.

A particle of mass 2kg start motion form rest on a circular path of radius r=4m with constant tangential acceleration `4 ms^(-2)`. Find the net work done on the particle in initial 1 second.A. 16JB. 25JC. 30JD. 6J

Answer» `w=(1)/(2)mv^(2)=(1)/(2)xx4^(2)`
14054.

If a particle of mass m start from along curved circular path shown in figure with constant tangential acceleration a, then net force at B on the particle has the magnitude : A. zeroB. `2ma sqrt(1 + pi^(2))`C. `ma sqrt(1 + pi^(2))`D. `ma pi sqrt(1 + pi)`

Answer» Correct Answer - C
`F_("net") = ma_("total") = m sqrt(a_(t)^(a) + a_(c )^(2))`
`a_(t) = a`
`a_(c ) = (v^(2))/(R )`
`v^(2) = 0 + 2a ((pi R)/(2))`
`u = sqrt(pi R a) " " rArr a_(c ) = (pi R a)/(R ) = pi a`
14055.

Define precision and accuracy. Explain with one example?

Answer»

The accuracy of a measurement is a measure of how close the measured value is to the true value of the quantity. Precision of a measurement is a closeness of two or more measured values to each other.

The true value of a certain length is near 5.678 cm. In one experiment, using a measuring instrument of resolution 0.1 cm, the measured value is found to be 5.5 cm. In another experiment using a measuring instrument of greater resolution, say 0.01 cm, the length is found to be 5.38 cm. We find that the first measurement is more accurate as it is closer to the true value, but it has lesser precision. On the contrary, the second measurement is less accurate, but it is more precise.

14056.

`U = 2x^(3) - 2x^(3) - 6x^(2) + 5x`, where x is in metres and U is the potential energy which depends on x. Selsct the correct option.A. There are two stable equilibrium positions, at `x = (1 +- (1)/(sqrt6)) m`B. `x = (1 + (1)/(sqrt6)) m` is stable equilibrium position.C. `x = (1 - (1)/(sqrt6)) m` is stable equilibrium position.D. `x = (1 + (1)/(sqrt6)) m` is unstable equilibrium position.

Answer» Correct Answer - B
`U = 2x^(3) - 6x^(2) + 5x`
at eq., `(dU)/(dx) = 6 x^(2) - 12 x + 5 = 0`
`x = 1 pm (1)/(sqrt6)`
for stable eq., `(d^(2)U)/(dx^(2)) gt 0`
`(d^(2)U)/(dx^(2)) = 12 x - 12`
`(d^(2)U)/(dx^(2)) gt 0` at `x = 1 + (1)/(sqrt6)`
& `(d^(2)U)/(dx^(2)) lt 0` at `x = 1 - (1)/(sqrt6)`
14057.

Four particles of masses 1 kg, 2 kg, 3 kg, and 4 kg are situated at the corners of a square and moving at speed `3 ms^(-1), 4 ms^(-1), 1 ms^(-1)` and `2 ms^(-1)` respectively. Each particle maintains a direction towards the particle at the next comer symmetrically. The momentum of the system at this instant is A. `3 kg ms^(-1)`B. `5 kg ms^(-1)`C. `6 kg ms^(-1)`D. Zero

Answer» Correct Answer - D
`vec(P)_("system") = m_(1) vec(v)_(1) + m_(2) vec(v)_(2) + m_(3) vec(v)_(3) + m_(4)vec(v)_(4)`
`= 4 (-2 hat(j)) + 3 (-hat(i)) + 4 (+2 hat(j)) + 1 (+3 hat(i)) = 0`
14058.

A particle starts from rest x = - 2.25 m and moves along the x - axis with the v - t graph as shown. The time when the particle crosses the origin is : A. 0.5 sB. 1 sC. 1.5 sD. 2 s

Answer» Correct Answer - B
When particle reaches the origin, then
`s = vec(x)_(f) - vec(x)_(i) = 2.25m`
So, area of v-t curve = 2.25 m
14059.

The potential energy of a particle is determined by the expression `U=alpha(x^2+y^2)`, where `alpha` is a positive constant. The particle begins to move from a point with coordinates `(3, 3)`, only under the action of potential field force. Then its kinetic energy T at the instant when the particle is at a point with the coordinates `(1,1)` isA. `8 alpha`B. `24 alpha`C. `1 b alpha`D. zero

Answer» Correct Answer - C
M.E. = U + K = constant
`U_(i) + K_(i) = U_(f) + K_(f)`
`alpha (3^(2) + 3^(2)) + 0 = alpha (1^(2) + 1^(2)) + K_(f)`
14060.

A college offers 7 courses in the morning and 5 in the evening. Find the number of ways a student can select exactly one course, either in the morning or in the evening.

Answer»

The student has 7 choices from the morning courses out of which he can select one course in 7 ways. For the evening course, he has 5 choices out of which he can select one course in 5 ways. 

Hence, he has total number of 7 + 5 = 12 choices.

14061.

∫sin9 x dx for x ∈ [-π/2,π/2] equals (a) -1(b) 1(c) 0(d) none of these

Answer»

Answer is (c) 0

14062.

The angle which the tangent to the curve y = x2 at (0,0) makes with the positive direction of x-axis is(a) 90°(b) 0°(c) 45°(d) 30°

Answer»

Answer is (b) 0°

14063.

The probability of getting a doublet with 2 dice is(a) 2/3(b) 1/6(c) 5/6(d) 5/36

Answer»

Answer is (b) 1/6

14064.

The value c in Rolle's theorem for f(x) = x2 - 1 in interval (-1,1) is (a) 1/2(b) 0(c) 1/4(d) none of these

Answer»

Answer is (b) 0

14065.

If vector(2i + j + k), vector(6i - j + 2k) and vector(14i - 5j + 4k) be the position vectors of the points A,B and C respectively, then(a) A,B,C are collinear(b) A,B,C are non-collinear(c) vector AB perpendicular BC(d) none of these 

Answer»

Answer is (a) A,B,C are collinear

14066.

In a frequency distribution table with 12 classes, the class-width is 2.5 and the lowest class boundary is 8.1, then what is the upper class boundary of the highest class?

Answer» Correct Answer - 38.1
14067.

The distributions X and Y with total number of observations 36 and 64, and mean 4 and 3 respectively are combined. What is the mean of the resulting distribution X + Y?

Answer» Correct Answer - 3.36
14068.

A data has 25 observations arranged in a descending order. Which observation represents the median?

Answer» Correct Answer - 13th
14069.

While calculating the mean of a given data by the assumed-mean method, the following values were obtained: `A=25. Sigmaf_1d_1=110,Sigmaf_1=50` Find the mean.

Answer» Correct Answer - 27.2
14070.

For a certain distribution, mode and median were found to be 1000 and 1250 respectively. Find mean for this distribution using an empirical relation

Answer» Correct Answer - 1375
14071.

Find the class marks of classes 10-25 and 35-55.

Answer» Correct Answer - 17.5,45
14072.

Find the value of for which \(f(x) = \begin{cases} kx + 5 ,& When \,x\leq2.\\ x-1 ,& When\, x >2 \end{cases}\) is continuous at x = 2.

Answer»

\(f(x) = \begin{cases} kx + 5 ,& When \,x\leq2.\\ x-1 ,& When\, x >2 \end{cases}\)

Left hand limit of function f(x) at = 2 is f(2) = \(\lim\limits_{x \to2^-}\)f(x) = \(\lim\limits_{x \to2}\)(kx + 5) = 2k + 5.

Right hand limit of function f(x) at = 2 is f(2+) = \(\lim\limits_{x \to2^+}f(x)\) = \(\lim\limits_{x \to2}\)(x-1) = 2 - 1 =1.

Since, we know that if function f(x) is continuous at = 2, then left hand limit of function f(x) at x = 2 is equals to the right hand limit of function f(x) at = 2 which is also equals to f(2). 

i.e., f(2 ) = f(2 +) = (2). 

Therefore, 2k + 5 = 1 

⇒ 2k = −4 

⇒ k = −2.

Hence, k = -2 for which the function \(f(x) = \begin{cases} kx + 5 ,& When \,x\leq2.\\ x-1 ,& When\, x >2 \end{cases}\) is continuous at x = 2.

14073.

Cards marked with numbers 13, 14, 15,……,60 are placed in a box and mixed thoroughly. One card is drawn at random form the box. Find the probability that the number on the card is a number which is a perfect square.

Answer»

Since,

Cards marked with numbers 13, 14, 15, ….60. 

Therefore,

Total number of cards = 60-12 = 48 

Perfect squares lie in the sequence 13, 14…...,60 are 16, 25, 36, 49. 

Total number of perfect squares lies in 13 – 60 range = 4. 

Hence,

Probability of getting perfect squares 

\(\frac{Total\,perfect\,squares\,in\,the\,range\,13-60}{Total\,number\,of\,cards}\) 

\(\frac{4}{48}\) 

\(\frac{1}{12}\).

14074.

A fair die is thrown once. The probability of even composite number is (a) 0(b) 1/3(c) 3/4(d) 1

Answer»

Correct answer is: (b) 1/3

P(even composite no) =2/6

=1/3

14075.

A fair die is thrown once. A person will get Rs. 5 if the die results in multiplying 3. Otherwise he loses Rs 2. Find his expectations.

Answer»

Let X denote expected amount, which takes the values X : 5 and - 2. With respective probabilities as:

P(x = 5) = P(getting muItiple of 3)

= 2/6 ; {i.e. 3,6}

P(x = 2) = 4/6; {i. e.1,2,4,5}

The probability of distribution is

X5-2
p(X)2/64/6

Expected amount: E(X) = ΣX.P(X)

= 5 x 2/6 -2 x 4/6 = 1 - 67 - 1.33 

= 0.34 i.e. 34 paise gain.

14076.

Find the probability that a non – leap year contains (i) 53 Sundays (ii) 52 Sundays only.

Answer»

A non - leap year contains 365 days 52 weeks and 1 day more.

(i) We get 53 sundays when the remaining day is Sunday.

Number of days in the week = 7

∴ n(S) = 7

Number of ways getting 53 Sundays. n(E) = 1

∴ P(E) = n(E)/n(S) = 1/7

∴ Probability of getting 53 Sundays = 1/7

(ii) Probability of getting 52 Sundays P(vector E) = 1 – P(E)

= 1 – 1/7 = 6/7.

14077.

For submitting tax returns, all resident males with annual income below Rs 10 lakh should fill up Form P and all resident females with income below Rs 8 lakh should fill up Form All people with incomes above Rs 10 lakh should fill up Form R, except non residents with income above Rs 15 lakhs, who should fill up Form S. All others should fill Form T. An example of a person who should fill Form T is (A) a resident male with annual income Rs 9 lakh (B) a resident female with annual income Rs 9 lakh(C) a non-resident male with annual income Rs 16 lakh  (D) a non-resident female with annual income Rs 16 lakh 

Answer»

Correct option   (B) a resident female with annual income Rs 9 lakh

Explanation:

Resident female in between 8 to 10 lakhs haven’t been mentioned. 

14078.

In a housing society, half of the families have a single child per family, while the remaining half have two children per family. The probability that a child picked at random, has a sibling is _____ 

Answer»

Let E1 = one children family 

 E2 = two children family and 

 A = picking a child then by Baye’s theorem, required probability is 

P(E2/A) = (1/2x)/(1/2 . x/2 + 1/2 .x) = 2/3 = 0.667

14079.

Fill in the blanksThe sum of the probabilities of all elementary events of an experiment is___. 

Answer»

(iv) The sum of the probabilities of all elementary events of an experiment is  Sum of probabilities of an experiment = 1.

14080.

The exports and imports (in crores of Rs.) of a country from 2000 to 2007 are given in the following bar chart. If the trade deficit is defined as excess of imports over exports, in which year is the trade deficit 1/5th of the exports?(A) 2005 (B) 2004 (C) 2007 (D) 2006

Answer»

Correct option (D) 2006

Explanation:

2004, (imports - exports)/exports = 10/70 = 1/7

2005,26/76 = 2/7

2006, 20/100 = 1/5

2007, 10/100 = 1/11

14081.

For matrices of same dimension M, N and scalar c, which one of these properties DOES NOT ALWAYS hold? (A) (MT)T = M (B) (cMT)T = c(M)T (C) (M + N)T = MT + NT  (D) MN = NM

Answer»

Correct option (D) MN = NM

Explanation:

Matrix multiplication is not commutative in general.

14082.

You are given three coins: one has heads on both faces, the second has tails on both faces, and the third has a head on one face and a tail on the other. You choose a coin at random and toss it, and it comes up heads. The probability that the other face is tails is  (A) 1/4 (B) 1/3 (C) 1/2 (D) 2/3

Answer»

Correct option (B) 1/3

14083.

In how many ways the letters of the word 'PIANO' can be arranged such that no consonant come together?1. 642. 723. 844. 96

Answer» Correct Answer - Option 2 : 72

Concept:

  • The ways of arranging n different things = n!
  • The ways of arranging n things, having r same things and rest all are different = \(\rm n!\over r!\)
  • The no. of ways of arranging the n arranged thing and m arranged things together = n! × m!
  • The number of ways for selecting r from a group of n (n > r) = nCr 
  • To arrange n things in an order of a number of objects taken r things = nPr  

 

Calculation:

For no consonants to be together the word can be formed as 

'1' A '2' I '3' O '4', where 1, 2, 3, 4 are the places where 2 consonants P and N could be placed

∴ Vowels arranged in = 3! ways

Ways of arranging consonants = 4P2

The total number of ways formed N = 3! × 4P2 

N = 6 × 12 = 72

14084.

Which of the following types of power have to be pre-justified; and, when the need and occasion arise, must very soon be post-justified ? 1. Reward power2. Coercive power3. Legitimate power4. Expert power5. Referent powerWhich of the above statements are correct ? 1. 1, 2 and 32. 1, 2 and 53. 2, 3 and 44. 3, 4 and 5

Answer» Correct Answer - Option 1 : 1, 2 and 3

Explanation:

  • Positional Power—Result of the manager's position within organization. 
  • Legitimate power—Manager's position within the organization and the authority that lies with that position.
  • Reward Power—People in power are after able to give out rewards. Raises, promotions, desirable assignments, training opportunities and simple compliments—these are all examples of rewards controlled by people "in power". 
  • Coercive Power—This source of power is also problematic and can be abused. Threats and punishment are common coercive tools.
  • Informational Power—Having control over information that others need or want puts you in a Powerful position.
  •  Personal Power—Is a source of influence and authority a person has over his or her followers. 
  • Expert Power—Power lay virtue of knowledge.
  • Referent Power—Power bestowed by virtue of love and respect.
  • Expert and referent power are by willful acceptance of others and therefore do not require either to be pre-justified or to be post-justified others are by virtue of perception of the powerful and may not be acceptable to others. 
14085.

Out of 3n consecutive natural numbers, 3 natural numbers are chosen at random without replacement. The probability that the sum of the chosen numbers is divisible by 3, isA. `(n(3n^(2)-3n+2))/(2)`B. `((3n^(2)-3n+2))/(2(3n-1)(3n-2))`C. `((3n^(2)-3n+2))/((3n-1)(3n-2))`D. `(n(3n-1)(3n-2))/(3(n-1))`

Answer» Let the sequence of 3n consecutive integras begins with m. Then 3n consective integers are `m, m+1, m+2, .....m+(3n+1)`
3 integers from 3n can be selected in `.^(3n)C_(3)` ways
`:.` Total number of outcomes `=.^(3n)C_(3)`
Now 3n integers can be divided into 3 groups.
`G_(1)` : n numbers of from 3p
`G_(2)` : n numbers of form 3p+1
`G_(3)` : n number of form 3p+2
The sum of 3 integers chosen from 3n integers will be divisible by 3 if either all the three are from same group of one integer from each group. The number of ways that the three integers are from same group is `.^(n)C_(3)+.^(n)C_(3)+.^(n)C_(3)` and number of ways that the integers are from different group is `.^(n)C_(1)xx.^(n)C_(1)xx.^(n)C_(1)`
`:.` Favourable cases `=(.^(n)C_(3)+.^(n)C_(3)+.^(n)C_(3))+(.^(n)C_(1)xx.^(n)C_(1)xx.^(n)C_(1))`
`:.` Required probability = `(3.^(n)C_(3)+(.^(n)C_(1))^(3))/(.^(3n)C_(3))`
`=(3n^(2)-3n+2)/((3n-1)(3n-2))`
14086.

Find the transformed equation of the straight line 2x – 3y + 5 = 0, when the origin is shifted to the point (3, -1) after translation of axes.

Answer»

Let coordinates of a point P changes from (x, y) to (X, Y) in new coordinate axes whose origin has the coordinates h = 3, k = -1. Therefore, we can write the transformation formulae as x = X + 3 and y = y – 1.

Substituting, these values in the given equation of the straight line, we get 2(X + 3) – 3 (Y – 1) + 5 = 0 or 2X – 3Y + 14 = 0. Therefore, the equation of the straight line in new system is 2x – 3y + 14 = 0.

14087.

Find the transformed form of the equation 2x2 + 4xy  + 3y2 = 0 if the origin is shifted to the point (1, 1)

Answer»

Put x = X + 1, y = Y + 1 in the given equation.

We get

2(X + 1)2 + 4(X + 1)(X + 1)(Y + 1) + 3 (Y + 1)2 = 0

⇒ 2X2 + 4xy + 3Y2 + 8X + 10Y + 9 = 0

14088.

Find the transformed equation of 2x2 + 4xy + 5y2 = 0 when the origin is shifted to (3, 4) by translation of axes.

Answer»

Let (X, Y) be the new coordinates of the point (x, y).

=> x = X + 3, y = Y + 4

The transformed equation is 2(X + 3)2 + 4(X + 3)(Y + 4) + 5(Y + 4)2 = 0

=> 2(X2 + 6X + 9) + 4(XY + 4X + 3Y +12) + 5(Y2 + 8y + 16) = 0

=> 2X2 + 12X + 18 + 4XY + 16X + 12Y + 48 + 5Y2 + 40Y + 80 = 0

=> 2X2 + 4XY + 5Y2 + 28X + 52Y + 146 = 0

14089.

If `e^(-pi//2) lt theta lt pi //2 ` ,then =A. cos (log `theta) gt ` log (cos `theta`)B. cos (log `theta) lt` log (cos `theta`)C. cos (log `theta`) = log (cos `theta`)D. None of these

Answer» Correct Answer - A
since `e^(-pi//2) lt theta lt pi//2`
`implies "log" e^(-pi//2) lt "log" theta lt "log" pi//2`
`implies -(pi)/(2) lt "log" theta lt "log" (pi)/(2) lt 1 lt pi//2`
i.e., `-(pi)/(2) lt "log" theta lt (pi)/(2)`
But 0`lt` cos `theta lt 1`
so ,log (cos `theta) lt` log (1)
`implies ` log (cos `theta) lt 0`
Hence cos (log `theta) lt ` log (cos `theta`)
14090.

A natural number is chosen at random from the first 100 naturalnumbers. The probability that `x+(100)/x > 50`is`1//10`b. `11//50`c. `11//20`d. none of theseA. `(1)/(10)`B. `(11)/(50)`C. `(11)/(20)`D. None

Answer» Correct Answer - C
`( x + (100)/(x)) gt 50`
`(x - 25)^(2) gt 525`
`(x - 25) lt sqrt(525)` or `(x- 25) gt sqrt(525)`
`x lt (25 - sqrt(525)) ` or `x gt ( 25 + sqrt(525))`
`x lt (25 - 22.91)` or `x gt (25 + 22.91)`
`x lt 2.09` or `x gt 47.91`
`{:(x le 2 , or , x ge 48), ( darr , , darr), ((1","2) ,, (48","49"," 50"," .....99","100)):}`
Thus , the favourable number of case is (2 + 53) = 55
Hence , the required probability = `(55)/(100) = (11)/(20)`
14091.

A bag contains 5 apples and 7 oranges and another basket contains 4 apples and 8 oranges. One fruit is picked out from each basket. Find the probability that the fruits are both apples or both oranges.

Answer» Probability both are oranges or both are apples=`7/12xx8/12+5/12xx4/12=76/144`
14092.

Four boys picked 30 apples. The number of ways in which they can divide then if all the apples are identical isA. 5630B. 4260C. 5456D. None

Answer» Correct Answer - C
The number of ways to divide n identical things among r persons `=^(n + r -1)C_(r-1)` (By multinomial theorem)
n = 30 , r = 40
Req. no of ways `=^(30 + 4 -1)C_(4-1) = ^(33)C_(3) = (33 xx 32 xx 31)/(3 xx 2) = 5456`
14093.

Five persons entered a lift cabin on the ground floor of an 8-floor house. Suppose that each of them can leave the cabin independently at any floor beginning with the first. What is the total number of ways in which each of the five persons can leave the cabin at any of the 7 floors?

Answer»

Any one of the 5 persons can leave the cabin in 7 ways independent of other.
Hence the required number of ways = 7 × 7 × 7 × 7 × 7 = 75.

14094.

There are 6 multiple choice questions in an examination. How many sequences of answers are possible, if the first three questions have 4 choices each and the next three have 5 choices each?

Answer»

Each of the first three questions can be answered in 4 ways and each of the next three questions can be answered in 5 different ways.
Hence, the required number of different sequences of answers = 4 × 4 × 4 × 5 × 5 × 5 = 8000.

14095.

Name the protocol that is used to send emails.

Answer»

Answer is:

SMTP

SMTP - Simple Mail Transfer Protocol
14096.

In SQL, write the query to display the list of tables stored in a database.

Answer»

Answer is:

SHOW TABLES

14097.

What are the disadvantages of a lock stitch machine?

Answer»

Disadvantages of lock stitch machine are:

1. It leaves unfinished seam allowances 

2. Undesirable in fabrics that rave easily 

3. The operation need to be stopped frequently to rewind the bobbin.

14098.

Define “Serging”?

Answer»

A process by serging machine, it sews the fabric together, cuts off the fabric to make a smooth edge and wraps the thread around the edge in one operation.

14099.

Ms. Sharma runs a play school, she wants her teachers should be aware about ageappropriate play material, equipment’s and furniture for the classroom. She arranged a webinar for her teachers where they discussed – a) How is the space arranged, both indoors and outdoors? b) Are there clearly marked areas in which children may find the housekeeping, reading, and block materials? c) Is there enough space between the areas to walk around? She believes these features of a classroom will foster children’s freedom to select their own activities, which in turn develops the complexity of their play as well as encourages ongoing play. Size is also very important for the required & appropriate arrangement for the classes Make a detailed list of material and equipment’s required for Early childhood classroom.

Answer»

Early intervention and education for children. An inclusive curriculum for early childhood programs must support the right of all children, regardless of their abilities to participate enthusiastically in natural settings within their communities. Natural settings include, but are not limited to: home, preschool, nursery school. 

1. Putting the emotional needs of the students in the forefront 

2. The most fruitful way of building an inclusive learning environment comes from establishing meaningful connections with our students. 

3. Students must be engaged with information in a responsive learning environment that provides rich ways for students to progress from a very early stage 

4. Teachers need to use multiple approaches of learning

14100.

The number of ways to arrange the letters of the English alphabet, so that there are exactly 5 letters between a and b, is:1. 24P52. 24P5 × 20!3. 2 × 24P5 × 20!4. 2 × 24P5 × 24!

Answer» Correct Answer - Option 3 : 2 × 24P5 × 20!

Concept:

Combinations: The number of ways in which r distinct objects can be selected simultaneously from a group of n distinct objects, is:

nCr = \(\rm \frac {n!}{r!(n-r)!}\).

Permutations: The number of ways in which r objects can be arranged in n places (without repetition) is:

nPr = \(\rm \frac{n!}{(n - r)!}\).

  • nPr = nCr × r!.

  • n! = 1 × 2 × 3 × ... × n.

  • 0! = 1.

 

Calculation:

There are 26 letters in the English alphabet. If we separate the group (a, some 5 letters, b), we will be left with 19 more letters.

These 20 objects (1 group + 19 letters) can be arranged among themselves in 20! ways.

Since either a or b can be at the beginning or the end of the group of 7 letters (a, some 5 letters, b), the number of possible arrangements of the group  will be 2 × (1P1 × 5P5 × 1P1) = 2 × 5!.

Also, each group of 5 letters can be selected from the remaining 24 letters (except a and b) in 24C5 ways.

Required total number of ways = (2 × 5! × 24C5) × 20!

2 × 24P5 × 20!.