car A and car B enter an expressway at the same time and same place and head the same direction. car A travels at 70 miles per hour. If after 2.5 hours car B is 50 miles behind car A what is the speed of car B.
How to do it in your head:
They've separated 50 miles in 2.5 hours so they would separate
100 miles in 5 hours or 20 miles in 1 hour. So car B was going
20 mph slower or 50 mph.
How to do it by algebra:
rate × time = distance
car A 70 2.5 175
car B x 2.5 2.5x
The equation comes from:
= - 50
2.5x = 175 - 50
2.5x = 125
x = 50 mph
Edwin