T-shirts 22133

There were 40 boys in the school. They were branded with caps and t-shirts. Twenty-five boys had blue caps. Twenty boys had a blue cap and a yellow T-shirt.
a) How many boys had a yellow shirt?
b) How many boys did not have a blue cap?
c) How many boys only had a yellow shirt?

Correct answer:

a =  35
b =  15
c =  15

Step-by-step explanation:

$$\begin{gathered} P=M\cap Z \\ p=20 \\ m=25-p=25-20=5 \\ z=40-p-m=40-20-5=15 \\ a=p+z=20+15=35 \end{gathered}$$

$b=z=15$

$c=z=15$

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