# Trying to understand example problem on how to solve rates

### Trying to understand example problem on how to solve rates

Im studying these notes on how to solve rates. I dont understand how it's telling me to calculate it. Can someone explain where the 120 comes from in the screenshot?
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Where does the 120 come from?
Screenshot_20180627-155010.png (172.93 KiB) Viewed 171 times
Screenshot_20180627-154951.png (192.09 KiB) Viewed 171 times

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### Re: Trying to understand example problem on how to solve rat

Many people prefer working with whole numbers to fractions and when confronted with an equation involving fractions will try to get rid of them as soon as practical -- typically by multiplying both sides of the equation by the least common multiple of everything that appears in a denominator. In this case 120 is the LCM of 40 and 60 so multiplying by it converts an ugly fractions equation into a nice easy whole numbers equation.

phw

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