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A, B and C can do a job working alone in 50, 75 and 20 days respectively. They all work together for 4 days, then C quits. How many days will A and B take to finish the rest of the job?
- A20
- B30
- C18
- D24
Answer not set
Discussion 1
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CCommunity
Suppose unit work = 300 units (LCM of 50, 75 & 20)
∴ Work done by A in one day = 300/50 = 6
Work done by B in one day = 300/75 = 4
Work done by C in one day = 300/20 = 15
∴ Work done by (A + B + C) in 4 days = 4 × (6 + 4 + 15) = 100
C quits after 4 days.
∴ Remaining work after 4 days = 300 – 100 = 200 units
∴ Time taken by A and B together to complete 200 units = 200/(6 + 4) = 20 days
∴ Work done by A in one day = 300/50 = 6
Work done by B in one day = 300/75 = 4
Work done by C in one day = 300/20 = 15
∴ Work done by (A + B + C) in 4 days = 4 × (6 + 4 + 15) = 100
C quits after 4 days.
∴ Remaining work after 4 days = 300 – 100 = 200 units
∴ Time taken by A and B together to complete 200 units = 200/(6 + 4) = 20 days