Question
P, Q, R can do a piece of work in 40 days, 90 days, and
36 days, respectively. P started the work. Q joined him after 7 days. If R joined them after 8 days from the beginning, then for how many days did R work?Solution
LCM (40, 90, 36) = 360 Let the total work be the LCM of the time taken individually by the workers. Efficiencies, P does each day = 360 40 = 9 units Q does each day = 360 90 = 4 units R does each day = 360 36 = 10 units Let the total work be completed in K days. According to the question, 9 x K + 4 x (K-7) + 10 x (K - 8) = 360 23K= 468 K = 468/23 (K-8) =284/23 (K - 8) = 12(8/23) 
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