Jyoti can do 3/4 of a job in 12 days. Mala is twice as efficient as Jyoti. In how many days will Mala finish the job ?

Answer: Option B

Jyoti does $$\frac{3}{4}$$ unit of work in 12 days
Jyoti does 1 unit of work in
$$\begin{array}{rl}& =12\times \frac{4}{3}\\ & =16\text{ days}\end{array}$$
According to the question,

	Mala	:	Jyoti
Efficiency →	2	:	1
Time →	1	:	2
	↓×8		←↓×8
	8 days		16 days