Five men are working to complete a work in 15 days. After five days 10 women are accompanied by them to complete the work in next 5 days. if the work is to be done by women only then when could be the work will be over if 10 women have started it?

Let 1 man's 1 day work = m, 1 woman's 1 day work = w. 5m × 15 = 1 (total work). Work done in first 5 days = 5m × 5 = 1/3. Remaining work = 2/3. In next 5 days: (5m + 10w) × 5 = 2/3, so 5m + 10w = 2/15. Since 5m = 1/15, we get 1/15 + 10w = 2/15, so 10w = 1/15. If 10 women do the work alone: Time = 1/(10w) = 1/(1/15) = 15 days. Option B is correct.