Von went

Von went to a mall to buy some things for his school projects. He spent 5/8 of his money in a bookstore and 1/5 of the remainder in a grocery store. If he spent P120 in the grocery store, how much money did he have at the start? How much money did he have left?

Correct answer:

a =  1600 Php
b =  480

Step-by-step explanation:

$$\begin{gathered} \frac{1}{5}\cdot (a-\frac{5}{8}\cdot a)=120 \\ 1/5\cdot (a-5/8\cdot a)=120 \\ 3a=4800 \\ a=\frac{4800}{3}=1600 \\ a=1600=1600\text{Php} \end{gathered}$$

$$\begin{gathered} B=\frac{5}{8}\cdot a=\frac{5}{8}\cdot 1600=\frac{5\cdot 1600}{8}=\frac{8000}{8}=1000\text{Php} \\ G=\frac{1}{5}\cdot (a-B)=\frac{1}{5}\cdot (1600-1000)=120\text{Php} \\ b=a-B-G=1600-1000-120=480 \end{gathered}$$

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