Question

1. the school has 200 students: 120 boys and 80 girls. we need a sample of 20 students. how many boys and girls were selected?

Explanation:

Step1: Calculate proportion of boys

The proportion of boys in the population is $\frac{120}{200}=\frac{3}{5}$.

Step2: Calculate number of boys in sample

Number of boys in sample: $20\times\frac{3}{5} = 12$.

Step3: Calculate proportion of girls

The proportion of girls in the population is $\frac{80}{200}=\frac{2}{5}$.

Step4: Calculate number of girls in sample

Number of girls in sample: $20\times\frac{2}{5}=8$.

Answer:

12 boys and 8 girls.