Problema Solution
The Browns are moving across the country. Mr. Brown leaves 4.5 hours before Mrs. Brown. If he averages 70 mph and she averages 80 mph, how long will it take Mrs. Brown to overtake Mr. Brown?
Answer provided by our tutors
Mr. Brown leaves 4.5 before Mrs. Brown travelling at 70mph, so he is 315 miles away before she leaves.
His path can be written as 315 + 70t, where t is time in hours.
Mrs. Brown is travelling at 80mph, so her path can be written as 80t.
To find out when they meet, set the equations equal to each other and solve:
315 + 70t = 80t
10t = 315
t = 31.5
So it will take Mrs. Brown 31.5 hours to overtake Mr. Brown.