The ratio between a two-digit number and the sum of the digits of that number is 4 : 1. If the digit in the unit's place is 3 more than the digit in the ten's place, then the number is ?

Answer: Option B

Let the ten's digit be x
Then, units digit = x + 3
Number = 10x + (x + 3)
              = 11x + 3
Sum of digits = x + (x + 3)
                      = 2x + 3
$$\begin{array}{rl}& \therefore \frac{11x+3}{2x+3}=\frac{4}{1}\\ & \iff 11x+3=8x+12\\ & \iff 3x=9\\ & \iff x=3\end{array}$$
Hence, Required number
= 11x + 3
= 11 × 3 + 3
= 36