1.

Sum of first 65 terms in an AP is 3300 find its 28 th term​

Answer»

Correct Question :

The sum of first 55 terms in an AP is 3300 find its 28TH term

Answer :

28th term = 60

Step-by-step explanation :

Given,

The sum of first 55 terms in an AP is 3300

In an AP, sum of n terms is given by

 \boxed{\bf S_n=\frac{n}{2}[2a+(n-<klux>1</klux>)d]}

where

Sₙ - sum of n terms

 n - number of terms

 a - first term

 d - common difference

Put Sₙ = 3300 and n = 55,

  \sf 3300=\frac{65}{2} [2a+(55-1)d]  

 3300 × 2 = 55 [2a + 54d]

   6600 = 55 [2a + 54d]

  6600/55 = 2a + 54d

    120 = 2a + 54d

    120 = 2(a + 27D)

    120/2 = a + 27d

      60 = a + 27d

We have to find the 28th term.

  i.e., a₂₈ = ?

NTH term of an AP is given by,

 \boxed{\bf a_n=a+(n-1)d}

Put n = 28,

 a₂₈ = a + (28 - 1)d

 a₂₈ = a + 27d

 a₂₈ = 60

Therefore, 28th term is 60


Discussion

No Comment Found

Related InterviewSolutions