A and B can do a work in 10 days and 15 days respectively. A starts the work and B joins him after 3 days. In how many days can they complete the remaining work?\nOptions:\n(A) 6 days\n(B) 2 days\n(C) 8 days\n(D) 4 1/5 days\n(E) 9 days OK. Let's think. Some random thoughts first:
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Work done by A in 3 days = 3/10\nRemaining work = 7/10\nWork done by both A and B in one day = 1/10 + 1/15 = 5/30 = 1/6\nRemaining work = 7/10 * 6/1 = 21/5 = 4 1/5 days. The answer: (D).
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