Question

The sum of the digits of a $2-$ digit number is $9$. If the tens digit is half of the ones digit, find the $2-$digit number.

Answer 1

Let $2$ digit number is ab

$a+b=9$ ……..$\left(1\right)$

$a=\frac{b}{2}$ …..$\left(2\right)$

Put $\left(2\right)$ in $\left(1\right)$

$\frac{b}{2}+b=9$

$\frac{\text{/}3b}{2}={\text{/}9}^3$

$b=6$

$\Rightarrow a=\frac{b}{2}=\frac{6}{2}=3$

$\therefore$ Number is $36$.