Question

In a two-digit number, the units digit is twice the tens digit. If 27 is added to the number, the digits interchange their places. Find the number.

• A. 63
• B. 36
• C. 69
• D. 96

Answer 1

The correct option is B 36

Let the digit in the units place be $y$ and digit in the tens place be $x$.

$\Rightarrow$ The number is $10x+y$

Given: $y=2x$.....(1)

and $10x+y+27=10y+x$....(2)

Substitute the value of $y$ in (2)

$\Rightarrow 10x+2x+27=10\left(2x\right)+x$ [$\because$ y = 2x]

$\Rightarrow 12x+27=21x\Rightarrow 9x=27$

$\Rightarrow x=3$

Substitute the value of $x=3$ in (1)

$\Rightarrow y=6$

$\therefore x=3andy=6$

Therefore, number is 36.