Two friends left school at the same time and drove in opposite directions. one friend averages 40 miles per hour and the other friend averages 35 miles per hour. when will they be 150 miles apart?

The two friends will be 150 miles apart, when the sum of the distances covered by the them is 150 miles.

distance = speed x time.
Let the time covered when they are 150 miles apart be x, then:
40x + 35x = 150
75x = 150
x = 150/75 = 2.

Therefore, the two friends will be 150 miles apart in 2 hours.

127 millimeters is the answer