Trying to understand example problem on how to solve rates

Trying to understand example problem on how to solve rates

Postby Needhelppleasehelp » Wed Jun 27, 2018 7:01 pm

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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Screenshot_20180627-155010.png
Where does the 120 come from?
Screenshot_20180627-155010.png (172.93 KiB) Viewed 73 times
Screenshot_20180627-154951.png
Screenshot_20180627-154951.png (192.09 KiB) Viewed 73 times
Needhelppleasehelp
 
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Re: Trying to understand example problem on how to solve rat

Postby phw » Fri Jun 29, 2018 9:53 pm

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.

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