Some carpenters promised to do a job in 9 days but 5 of them were absent and remaining men did the job in 12 day. The original number of carpenters was ?

Answer: Option B

Let there were N carpenters in the beginning
According to the question,
$$\frac{{\text{N}}_{\text{men}}\times 9_{\text{days}}}{{\text{1}}_{\text{work}}}=$$     $$\frac{{\left(\text{N}-5\right)}_{\text{men}}\times {12}_{\text{days}}}{{\text{1}}_{\text{work}}}$$
$$\begin{array}{rl}& \text{3N}=\text{4N}-20\\ & \text{N}=\text{20 men}\end{array}$$