Question

the ones digit of a two digit number is twice the tens digit when the number formed by reversing the digit is added to original number the sum is 99 find the original number

Answer 1

x is one's digit. y is ten's digit.
x=2y
10y+x+10x+y=99
11x+11y=99
x+y=9
2y+y=9
3y=9
y=3
x=6
The number is 36.

Answer 2

Answer:

Let the tens digit be y and the ones digit be x.

The original number = 10y + x

The reverse number = 10x + y

It is given that ones digit is twice the tens digit :]

➳ x = 2y ............[Equation (i)]

According to question now,

➳ 10x + y + 10y + x = 99

➳ 11x + 11y = 99

➳ 11 (x + y) = 99

➳ x + y = 99/11

➳ x + y = 9

➳ y = 9 - x.........[Equation (ii)]

Now, Substituting equation (ii) in equation (i) we get :

➳ x = 2 (9 - x)

➳ x = 18 - 2x

➳ 3x = 18

➳ x = 18/3

➳ x = 6

Putting x = 6 in equation (ii) we get :

➳ y = 9 - x

➳ y = 9 - 6

➳ y = 3

Therefore,

• The original number = 10y + x = 10(3) + 6 = 30 + 6 = 36