Cooking classes

Ms. Wright's two cooking classes are making a total of 60 sweet potato pies. Each pie requires 2 1/4 sweet potatoes. Her first class makes 1/3 of the total number of pies needed. Exactly how many sweet potatoes will her second class need in order to make the remaining pies?

Correct answer:

x =  90

Step-by-step explanation:

$$\begin{gathered} n=60 \\ a=\frac{1}{3}\cdot n=\frac{1}{3}\cdot 60=\frac{1\cdot 60}{3}=\frac{60}{3}=20 \\ b=n-a=60-20=40 \\ o=2\frac{1}{4}=2+\frac{1}{4}=\frac{2\cdot 4+1}{4}=\frac{8+1}{4}=\frac{9}{4}=2\frac{1}{4}=2.25 \\ x=o\cdot b=\frac{9}{4}\cdot 40=\frac{9\cdot 40}{4}=\frac{360}{4}=90 \end{gathered}$$

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