Question

[Đặng Lan Phương]

It takes Tom 4 hours to built a fence. If he hires Jack to help him, together they can do the job in just 3 hours. If jack built the same fence alone, how long would it take him?

Answer 1

[Cô Hoàng Huyền]

In a hour, Tom and Jack can do: \(\frac{1}{3}\) (the job)

In a hour, Tom can do: \(\frac{1}{4}\) (the job)

So in a hour, Jack can do: \(\frac{1}{3}-\frac{1}{4}=\frac{1}{12}\) (the job)

Thus, if Jack built the same fence alone, it would take 12 hours.

Answer 2

[Lương Quỳnh Trân]

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