Two trucks leave from the same truck stop at the same time. One travels east on interstae 80 and the other travels west. The eastbound truck averages 40 miles per hour, and the westbound truck averages 50 miles per hour. In how many hours will the trucks be 300 miles apart?
There are two ways to do this problem,
1. Using rate of separation rate and the formula time = distance÷time
2. By using chart and algebra
Let's look at both ways.
1. Their rate of separation is 40+50 = 90 mph, so time = distance÷time
= 900÷30 = 3 hours. That's the easy way but your teacher may
not accept it since it doesn't use an equation, but just basic math.
2. Make this chart:
distance rate time
Eastbound truck
Westbound truck
Both trucks travel the same length of time, so
let that time be t.
Fill that in for the times for both trucks:
distance rate time
Eastbound truck t
Westbound truck t
Fill in the two speeds
distance rate time
Eastbound truck 40 t
Westbound truck 50 t
Us distance = rate×time to fill in the distances
distance rate time
Eastbound truck 40t 40 t
Westbound truck 50t 50 t
The total of their distances is to be 300 miles, so we form the
equation this way:
Eastbound truck's distance + Westbound truck's distance = 300
40t + 50t = 300
90t = 300
t =
t = hours.
Edwin