Problema Solution
It took Betty 5.4 hours to drive to her mothers house on Thursday. On her return trip on friday the trip took 6 hours. Her average speed on friday was 6 mph slower than on thursday. What was her average speed on friday?
Answer provided by our tutors
let
v1 = the speed on the way to her mother (on Thursday)
v2 = the speed of the return trip (on Friday)
t1 = 5.4 hr the time of the trip to her mother
t2 = 6 hr the time of the return trip
since v = d/t follows d = v*t
Betty traveled the same distance on the way to her mother and on the way back thus we have:
v1*t1 = v2*t2
5.4v1 = 6v2
Her average speed on Friday was 6 mph slower than on Thursday:
v2 = v1 - 6
by solving the system of equations:
5.4v1 = 6v2
v2 = v1 - 6
we find:
v1 = 60 mph
v2 = 54 mph
click here to see the step by step solution of the system of equations:
Betty's average speed on Friday was 54 mph.