Track suits

There are 100 tracksuits in a box. The sports shop sold 3/10 of the tracksuits on Monday, 1/4 on Tuesday, and they sold 2/5 on Wednesday, and the rest on Thursday.

1. How many tracksuits did the shop sell on Thursday?
2. What fraction of the tracksuits did the shop sell on Thursday?

Correct answer:

d =  5
f =  1/20

Step-by-step explanation:

$$\begin{gathered} n=100 \\ a=\frac{3}{10}\cdot n=\frac{3}{10}\cdot 100=\frac{3\cdot 100}{10}=\frac{300}{10}=30 \\ b=\frac{1}{4}\cdot n=\frac{1}{4}\cdot 100=\frac{1\cdot 100}{4}=\frac{100}{4}=25 \\ c=\frac{2}{5}\cdot n=\frac{2}{5}\cdot 100=\frac{2\cdot 100}{5}=\frac{200}{5}=40 \\ d=n-a-b-c=100-30-25-40=5 \end{gathered}$$

$f=\frac{d}{n}=\frac{5}{100}=\frac{1}{20}=0.05$

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