A can finish a work in 15 days and B in 20 days. They work together for 6 days and then B leaves. In how many days will A finish the remaining work? MCQ with Answer and Explanation
A can finish a work in 15 days and B in 20 days. They work together for 6 days and then B leaves. In how many days will A finish the remaining work?
A. 4.5 days
B. 5 days
C. 3.5 days
D. 6 days
Answer: Option A
Solution (By JKSSB Mock Tests)
Total work = LCM(15, 20) = 60 units. Efficiency of A = 4, B = 3. Combined efficiency = 7. In 6 days, work done = 6 * 7 = 42 units. Remaining work = 60 - 42 = 18 units. Time taken by A to complete remaining work = 18 / 4 = 4.5 days.
A can do 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 will C alone finish the whole work?
Explanation:
Total work = LCM(20, 30) = 60 units. Efficiency of A = 3, B = 2. Combined efficiency = 5 units/day. In 7 days, work done = 7 * 5 = 35 units. Remaining work = 60 - 35 = 25 units. C's efficiency = 25 units / 10 days = 2.5 units/day. Days for C to complete total work = 60 / 2.5 = 24 days.
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