There are 250 boys and 150 girls in a school. If 60% of the boys and 40% of the girls play football, what percentage of the school plays football?

The number of boys who play football is $\frac{60}{100} \times 250 = 150$ and the number of girls who play football is $\frac{40}{100} \times 150 = 60$. Therefore a total of $150 + 60 = 210$ students in the school play football. There are $250 + 150 = 400$ students in the school, so the percentage that plays football is $\frac{210}{400} \times 100 = 52.5 \%$.