Question

Sheila leaves on a trip driving at 30 miles per hour. Two hours later, her sister Allison starts from the same location driving at 60 miles per hour. How long after Allison leaves home will she catch up to Sheila?


2 hours

4 hours

3 hours

5 hours

Answer 1

Then (t+2) = time S is on the road, when A catches up
:
We know that when A catches S, they will have traveled the same distance.
We can write a distance equation from that fact: Distance = speed * time
:
A's dist = S's distance
60t = 30(t+2)
60t = 30t + 60
60t - 30t = 60
30t = 60
t = 60/30
t = 2 hrs for A to catch up with S

Check our solution using the distance (S's time; 2 + 2 = 4 hrs)
30 * 4 = 120
60 * 2 = 120

Hope this helps!