A can do a piece of work in 10 days and B can do the same work in 15 days. If they work together on alternate days starting with A, in how many days will the work be completed? MCQ with Answer and Explanation
A can do a piece of work in 10 days and B can do the same work in 15 days. If they work together on alternate days starting with A, in how many days will the work be completed?
A. 13 days
B. 12 days
C. 11 days
D. 10 days
Answer: Option B
Solution (By JKSSB Mock Tests)
Total work = LCM(10, 15) = 30 units. Efficiency of A = 3, B = 2. In a 2-day cycle (A then B), work done = 3 + 2 = 5 units. Number of cycles required to complete 30 units = 30 / 5 = 6 cycles. Total days = 6 * 2 = 12 days.
A and B can complete a work in 15 days and 10 days respectively. They started the work together but B left after 2 days. In how many days will A complete the remaining work?
Explanation:
Total work = LCM(15, 10) = 30 units. Efficiency of A = 2, B = 3. Combined efficiency = 5 units/day. In 2 days, work completed = 2 * 5 = 10 units. Remaining work = 30 - 10 = 20 units. Time taken by A to complete remaining work = 20 / 2 = 10 days.
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