A school wants to investigate the amount of exercise students do. There are 1200 students at the school.
a Suggest a sensible number of students to be sampled.

100-200     Step-by-step explanation: yes 600 is half the students most of them are going to be in class

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.