Question

If 36 men can do a piece of work in 25 days, in how many days will 15 men do it?

Answer 1

Let x be the number of days in which 15 men can do a piece of work.

Number of men	36	15
Number of days	25	x

$$\begin{gathered} \mathrm{Since}\mathrm{the}\mathrm{number}\mathrm{of}\mathrm{men}\mathrm{hired}\mathrm{and}\mathrm{the}\mathrm{number}\mathrm{of}\mathrm{days}\mathrm{taken}\mathrm{to}\mathrm{do}\mathrm{a}\mathrm{piece}\mathrm{of}\mathrm{work}\mathrm{are}\mathrm{in}\mathrm{inverse}\mathrm{variation},\mathrm{we}\mathrm{have}: \\ 36\times 25=x\times 15 \\ \Rightarrow x=\frac{36\times 25}{15} \\ =\frac{900}{15} \\ =60 \\ \mathrm{Thus},\mathrm{the}\mathrm{required}\mathrm{number}\mathrm{of}\mathrm{days}\mathrm{is}60. \end{gathered}$$