3 men and 7 women can do a job in 5 days, while 4 men and 6 women can do it in 4 days. The number of days required for a group of 10 women working together, at the same rate as before, to finish the same job in ?

Answer: Option D

(3 men + 7 women) × 5 days = (4 men + 6 women) × 4 days
1 men = 11 women
∴ 3 men + 7 women
(3 × 11) women + 7 women
= 40 women
40 women can do a work in 5 days
1 women can do a work in (5 × 40) days
10 women can do a work in = $$\frac{5\times 40}{10}$$ = 20 days