A can finish a work in 20 days and B in 30 days. They work together for 7 days and then both leave. Then C alone finishes the remaining work in 10 days. In how many days can C alone finish the full work? MCQ with Answer and Explanation
A can finish a work in 20 days and B in 30 days. They work together for 7 days and then both leave. Then C alone finishes the remaining work in 10 days. In how many days can C alone finish the full work?
A. 25 days
B. 20 days
C. 24 days
D. 30 days
Answer: Option C
Solution (By JKSSB Mock Tests)
Total work = LCM(20, 30) = 60 units. Efficiency of A = 3, B = 2. Combined efficiency = 5 units/day. In 7 days, work completed = 7 * 5 = 35 units. Remaining work = 60 - 35 = 25 units. C takes 10 days to do 25 units, so efficiency of C = 25 / 10 = 2.5 units/day. Time taken by C alone for full work = 60 / 2.5 = 24 days.
A can do a piece of work in 10 days, B in 15 days. They work together for 2 days and then A leaves. In how many days will B complete the remaining work?
Explanation:
Total work = LCM(10, 15) = 30 units. Efficiency of A = 3, B = 2. Combined efficiency = 5 units/day. In 2 days, work completed = 2 * 5 = 10 units. Remaining work = 30 - 10 = 20 units. Time taken by B to complete remaining work = 20 / 2 = 10 days.
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