C can complete a work in 10 days, and D can complete the same work in 15 days. If they work together

A. 1/3

B. 1/4

C. 1/5

D. 1/2

E. None of the above

Answer: A. 1/3

C and D together can complete 1/10 + 1/15 = 1/6 of the work in one day. In 5 days, they complete 5/6 of the work, leaving 1/6 of the work remaining.

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