If 4 men or 6 women can do a piece of work in 12 days working 7 hours a day, how many days will it take to complete a work twice as large with 10 men and 3 women working together 8 hours a day ?

Answer: Option B

According to the question,
4 men = 6 women
2 men = 3 women
10 men + 3 women = 10 men + 2 men
10 men + 3 women = 12 men.....(i)
$$\frac{4_{\text{men}}\times {12}_{\text{days}}\times 7_{\text{hours}}}{{\text{1}}_{\text{work}}}=$$      $$\frac{{12}_{\text{men}}\times {\text{D}}_{\text{days}}\times 8_{\text{hours}}}{{\text{1}}_{\text{work}}}$$
$$\begin{array}{rl}& \text{After solving we get}\\ & \text{D}=7\text{ days}\end{array}$$