Question

a no. consists of two digit whose sum is 9 if 9 is subtracted from the no. the digits interchange their places find the no.

Answer 1

Let us assume, x and y are the two digits of a two-digit number.

Therefore, the two-digit number = 10x + y and the reversed number = 10y + x

Given:

x + y = 9 ---------1

Also given:

10x + y - 9 = 10y + x

9x - 9y = 9

x - y = 1 -----------2

Adding equation 1 and equation 2

2x = 10

x = 5

Therefore, y = 9 - x = 9 - 5 = 4

Therefore, the two digit number = 10x + y = 10*5 + 4 = 54