Ganga, Yamuna &Saraswati can complete a piece of

Solution

Let total work = LCM (30, 40 & 60) = 120 units Ganga's 1 day work = 120/30 = 4 units Yamuna's 1 day work = 120/40 = 3 units Saraswati'1 day work = 120/60 = 2 units (Ganga+Yamuna+Saraswati)'s 1 day work = 4+3+2 = 9 units So work done by all in 4 days = 9 `xx` 4 = 36 days, Now Ganga Left. Now for next few days, Yamuna & Saraswati worked together & then Yamuna left 12 days before the completion , it means Saraswati alone works in last 12 days. So Saraswati's work done in 12 days = 12`xx` 2 = 24 So work done in first 4 days & in last 12 days = 36+24 = 60 units Remaining work is done by (Yamuna+ Saraswati) in = 60/(3+2) = 60/5 = 12 days So total days to complete the work = 4+12+12 = 28 days