Question

Mr.Lee wants to survey 20 of the 210 students in seventh grade about the hours they slerp each night. He finds 2 of the 20 students surveyed sleep for 9 hours each night. About how many of the 210 seventh graders sleeo for 9 hours each night?​

Answer 1

21 students sleep for 9 hours each night

Solution:

Given that, Mr.Lee wants to survey 20 of the 210 students in seventh grade about the hours they sleep each night

He finds 2 of the 20 students surveyed sleep for 9 hours each night

Therefore, 2 out of 20 students sleep for 9 hours each night

Find out the percentage of 2 out of 20

$\rightarrow \frac{2}{20} \times 100 = 10 \%$

Thus 10 % of 210 students sleep for 9 hours each night

Find out 10 % of 210

$\rightarrow 10\% \text{ of } 210\\\\\rightarrow 10 \% \times 210\\\\\rightarrow \frac{10}{100} \times 210\\\\\rightarrow 21$

Thus 21 students sleep for 9 hours each night