## Prealgebra (7th Edition)

$\frac{1}{25}$
The table shows 3 with the AB+ blood type and 1 with the AB- blood type, so 4 ($3+1$) have type AB. The whole set of blood donors contained 100. $\frac{4}{100}=\frac{4\div4}{100\div4}=\frac{1}{25}$