Question
βAβ, βBβ and βCβ can complete a piece of
work in 60 days, 120 days and 80 days respectively. βAβ and βBβ started the work together but βAβ left the work after 15 days. Now βCβ joined the work and then after 9 days βBβ is replaced by βAβ. Find the time taken to complete the rest of the work by βAβ and βCβ together.Solution
Let total amount of work = 240 units (LCM of 60, 120 and 80) Amount of work done by βAβ in one day = 240/60 = 4 units Amount of work done by βBβ in one day = 240/120 = 2 units Amount of work done by βCβ in one day = 240/80 = 3 units Amount of work done by βAβ and βBβ together in 15 days = 15 Γ 6 = 90 units Amount of work done by βBβ and βCβ together in 9 days = 9 Γ 5 = 45 units Remaining work = 240 β 90 β 45 = 105 units Time taken by βAβ and βCβ together to complete the remaining work = 105/7 = 15 days
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