Midpoint = (x1 + x2) / 2, (y1 + y2)/2
(-2,1)....x1 = -2 and y1 = 1
(4,-1)...x2 = 4 and y2 = -1
time to sub
m = (-2 + 4) / 2 , (1 + (-1) / 2
m = (2/2), (0/2)
m = (1,0) <==
y = -x + 1.....(1,0)...x = 1 and y = 0
0 = -1 + 1
0 = 0 (correct)
so the midpoint M (1,0) lies on the line since its coordinates satisfy the equation <===
The sample % of these two populations would be 100/size (of student body at each school) x 100 so this would compare the two student bodies preferences for the particular type of candy bar. However, the actual % of the whole student body at each school would be a factor also. If the high school only had 200 students then this would be 50% representative but if the middle school had say 500 students this would only be 20% representative so this would have to be taken into account too. It might be more representative to have the same % of the student bodies respectively for the sample.
The answer is : 1:6 repeating
