Question

the sum of the digits of a two digit no.is 7 .when the digits are reversed then no. Is decreased by 9 find the no.

Answer 1

Step-by-step explanation:

Number: xy

x + y = 7--> x = 7-y

10y + x = 10 x + y + 27

Simplify:

9y = 9x + 27

9y = 9(7-y) + 27

9y = 63 - 9y + 27

18y =90

y = 5

x = 2

The number is 25

Answer 2

Answer:

34

Step-by-step explanation:

Let the one's digit be x

and ten's digit be y

Number = 10y + x

Reverse = 10x + y

Now,

x + y = 7. _ eqn. 1

10y + x -9= 10x + y

9y - 9x= 9

9(y-x) = 9

y - x = 1. _ eqn. 2

Adding 1 & 2,

2x= 8

x = 4

y = 7- x

y = 3

Number= 10y + x

Number = 34

Hope it helps