1.

A three digit number is equal to 17 times the sum of its digits; If the digits are reversed, the new number is 198 more than the old number ; also the sum of extreme digits is less than the middle digit by unity. Find the original number.​

Answer»

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Let the digit in hundreds place be x and that in unit place be y.

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

H ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀x

T ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀x + y + 1

unit⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀y

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

\implies the three digit number is 100x + 10(x + y + 1) + y

= 100x + 10x + 10y + 10 + y = 110x + 11Y + 10

the SUM of the digits in the given number = x + (x + y + 1) + y = 2x + 2y + 1

From first condition

Given number = 17 ´ (sum of the digits)

\implies 110x + 11y + 10 = 17 ´ (2x + 2y + 1)

\implies 110x + 11y + 10 = 34x + 34y + 17

\implies 76x - 23y = 7 . . . (I)

The number obtained by reversing the digits

= 100Y + 10(x + y + 1) + x = 110y + 11x + 10

Given number = 110x + 11y + 10

From 2nd condition, Given number + 198 = new number.

110x + 11y + 10 + 198 = 110y + 11x + 10

99x - 99y = -198

\implies x - y = -2

\implies x = y - 2 . . . (II)

Substitute this value of x in equation (I).

\implies 76(y - 2) - 23y = 7

\implies 76y - 152 - 23y = 7

\implies 53y = 159

\implies y = 3

\implies the digit in units place is = 3

Substitute this value in equation (II)

\implies x = y - 2

\implies x = 3 - 2 = 1

\implies x = 1

\implies The digit in hundred’s place is 1

the digit in ten’s place is 3 + 1 + 1 = 5

\implies the number is 153.



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