Question

A two-digit number is thrice the sum of the digits. If 9 is subtracted from the number, it becomes twice the sum of the digits. Find the digit in the unit's place.

पर्याय

• 6

• 7

• 5

• 4

Answer 1

7

Explanation:

Let the no. be xy,

It's value = 10x + y  ......[e.g. 13 = 1 × 10 + 3]

10x + y = 3(x+ y)

7x = 2y  ......(i)

10x + y – 9 = 2(x + y)

⇒ 10x + y – 9 = 2x + 2y

⇒ 8x = y + 9

`8(2/7 y) = y + 9`  ......[From (i)]

⇒ `16/7 y - y` = 9

⇒ `9/7 y` = 9

⇒ y = 7, x = 2

Hence, number is 27 and Unit's place digit = 7