30 I believe, sorry if I am wrong, I am bad at math and history.
The language art teacher wants to know the opinion of the ENTIRE school, so it would be fair if the teacher takes a sample from the ENTIRE school population. She can use the stratified sampling method where she can take a proportionate sample from each grade.
Correct answer: All students in each grade
4.56 / 3.42 = 1.333 m per second (or 1 1/3m per second)