Question

The sum of two digits of a two digit number is 15,if 9 is added to the number the digits are reversed. What is the number?

Answer 1

Step-by-step explanation:

Let the tens no = y or 10y

and once no = x

so,

y + x =15. ........1

10y + x + 9= 10x + y.

or

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

By elimination method

y + x = 15

y - x = 1

+. -. +

_______________

2y = 16

y=16 ÷ 2

y=8

putting the value of y in 2

8 - x = 1

-x = - 7

x = 7

so,

no = 10y + x

=. 10 × 8 + 7

= 80 + 7

=. 87