A and B can complete a piece of work in 12 and 18 days respectively. They begin the work together, but A leaves 4 days before the completion of the work. For how many days did A and B work together? MCQ with Answer and Explanation
A and B can complete a piece of work in 12 and 18 days respectively. They begin the work together, but A leaves 4 days before the completion of the work. For how many days did A and B work together?
A. 6 days
B. 5 days
C. 4.4 days
D. 5.6 days
Answer: Option D
Solution (By JKSSB Mock Tests)
Total work = LCM(12, 18) = 36 units. Efficiency of A = 3, B = 2. Let total days be x. B works for x days, A works for (x - 4) days. 3(x - 4) + 2x = 36 => 3x - 12 + 2x = 36 => 5x = 48 => x = 9.6 days. A and B worked together for x - 4 = 9.6 - 4 = 5.6 days.
Explanation:
Let efficiency of B = 1, then efficiency of A = 2. Combined efficiency = 3. Total work = 14 * 3 = 42 units. Time taken by A alone = 42 / 2 = 21 days.
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