A man can do a work in 20 days and a woman in 15 days. If they work on it together for 5 days, then the fraction of the work that is left-

Question: A man can do a work in 20 days and a woman in 15 days. If they work on it together for 5 days, then the fraction of the work that is left-

Solution:
Man's 1 day's work = 1/20
Woman's 1 day's work = 1/15

∴ (Man + woman)'s 1 day's work = (1/20) + (1/15) = (3 + 4)/60 = 7/60
∴ (Man + woman)'s 5 day's work = (7/60) × 5 = 7/12

Thus, Remaining work = 1 - (7/12) = (12 - 7)/12 = 5/12

∴ The fraction of the work that is left = 5/12