20 women work for 4 days on a certain project and complete one-tenth of it. 15 men work for the next 'X' days and complete one-fifth of it, If after (4+X) days, 20 women and 15 men work together and complete the remaining work in 12 days, then how many days will 15 men take to complete the whole work ?
20 Women's 1 day work=1/(4*10)=1/40
15 men's 1 days work=1/(X*5)=1/(5X)
After total (4+X) days, work comleted=1/10 + 1/5=3/10 and remaining work=7/10
As 20 women and 15 men complete the remaining work in 12 days, so their 1 day work=(1/12)*(7/10)=7/120
Comparing 1 day's work of 20 women and 15 men=1/40 + 1/(5X)=7/120
(X+8)/(40X)=7/120
Solving, we get X=6
.'. 1 day's work of 15 men=1/(5*6)=1/30
Hence, 15 men can complete the whole work in 30 days.
Correct Option 2)