Question

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

Answer 1

Let ten’s digit =$x$

Unit digit = $y$

Number = $10x+y$

Given $x=2y---\left(1\right)$

$10x+y+10y+x=66$

$11y+11x=66$

$y+x=6$

From eq $\left(1\right)$

$y=2$

$x=4$

Number $=42$