Set it up like this
[tex] \frac{160}{4} = \frac{?}{1} [/tex]
You know you need it to be in one minute, so at the bottom where the minutes are, you put the 1.
Cross multiply, meaning you multiply the numbers that are across. In this case, it is 160 X 1.
You get 160, and then you divide it by the "bottom" number, in this case 4.
The answer for the "?" is 40.
