The task is to generate the correct answer for a given math problem.

Q: Problem: a man can do a piece of work in 7 days , but with the help of his son , he can finish it in 3 days . in what time can the son do it alone ?

A: 4 1 / 5
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Q: Problem: the ratio of three numbers is 2 : 3 : 4 and their sum is 180 . the second number of the three numbers is ?

A: 60
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Q: Problem: if the cost price of 24 chocolates is equal to the selling price of 16 chocolates , the gain percent is :

A:
50 %
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