A can do a work in 16 days and B can do it in 24 days. If they work together for 8 days, how much work is left to be done?

Answer: B. 1/3
In 8 days, A and B together complete 8*(1/16 + 1/24) = 8*(5/48) = 5/6 of the work. Thus, 1 - 5/6 = 1/6 of the work is left.
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