Concept: The question tests on the area of Rates(Time and Work)
Solution:
12 men take 36 days
12 men in 1 day do 1/36th of the work
1 man in 1 day does 1/12∗36
8 men in 1 day does 8∗1/12∗36=1/54
18 women take 60 days
18 women in 1 day do 1/60 th of the work
1 woman in 1 day does 1/18∗60
20 women in 1 day does 20∗1/18∗60=1/54
8 men and 20 women in 1 day does 1/54+1/54=1/27th of the work
Work done in 20 days = 20∗1/27=20/27 th work
The remaining work = 1 – 20/27=7/27
Using the concept of MAN DAYS = M1∗T1/W1=M2∗T2/W2
M1 = 1, T1 = 1, W1 = Work done by 1 woman in 1 day1/18∗60
M2 = x, T1 = 4, W2 = Work done by x woman in 4 days to finish7/27th of the work
1∗1/(1/18∗60)=x∗4/(7/27)
x=70
Option A