Question

9. A number consists of two digits whose sum is 7. If 45 is added to the number, the digits are reversed. Find the
number.​

Answer 1

Digits :

Once = x

Tense = y

so, Number = 10 y + x

According to the question :

x + y = 7 .......... ( 1 )

Then :

45 is added to ( 10 y + x ) , it will be reversed .

so,

10 y + x = 45 = 10 x + y

= 45 = 10 x + y - 10 y - x

= 45 = 9x - 9y

= 45 = 9 ( x - y )

= ( x - y ) = 45 / 9

= ( x - y ) = 5 ......... ( 2 )

1 st and 2 nd Equation :

x + y = 7

x - y = 5 ' y ' will be cancelled

2x = 12

x = 12 / 2

x = 6.

then,

x + y = 7

6 + y = 7

y = 7 - 6

y = 1

Therefore , The number is 16 .