Tapas works twice as fast as Mihir. If both of them together complete a work in 12 days, Tapas alone can complete it in ?

Answer: Option B

	Tapas	:	Mihir
Efficiency units/day	2	:	1

$$\begin{array}{rl}& \text{T}+\text{M complete in 12 days}\\ & \text{Total work }\\ & =12\times \left(2+1\right)\\ & =36\text{units}\end{array}$$
Tapas alone complete the whole work in
$$\begin{array}{rl}& =\frac{36}{2}\\ & =18\text{ days}\end{array}$$