Question

In a two digit number, digit at the ten's place is twice the digit at units's place. If the number obtained by interchanging the digits is added to the original number, the sum is 66. find the number.

Answer 1

Let the digit at the unit's place be x.

Digit at tens place = 2x

Original number = (2x)×10 + x = 21x

Number obtained by interchanging the digits = (x)×10 + 2x = 12x

From the given information,

$$\begin{gathered} 12x+21x=66 \\ \therefore 33x=66 \\ \therefore x=2 \end{gathered}$$
∴ The unit's digit = 2.
Tens Digit = 2 × 2 = 4.

Hence, the number is 42.