Question

the ones digit of a 2-digit number is twice the tens digit when the number formed by reserving the digits is added to the original number the sum is 99 find the original number

Answer 1

Let the tens digit be x

Let the one's digit be 2x

∴ The original number = 10x + 2x

= 12x

Let the number reversed be 10 * 2x + x

= 20x + x

= 21x

__________________________

According to the question,

12x + 21x = 99

33x = 99

x = $\dfrac{99}{33}$

x = 3

__________________________

The original number = 10x + 2x

= 10 * 3 + 2 * 3

= 30 + 6

= 36

___________________________

∴ The original number is 36

Answer 2

Let the tens digit be x

Let the one's digit be 2x

∴ The original number = 10x + 2x

= 12x

Let the number reversed be 10 * 2x + x
= 20x + x
= 21x

___________________
ATC,

12x + 21x = 99

33x = 99
x = \dfrac{99}{33}3399​
x = 3

__________________________

The original number = 10x + 2x

= 10 * 3 + 2 * 3

= 30 + 6

= 36