a car travels 40 mph for 20 miles 36 mph for 24 miles and 48

a car travels 40 mph for 20 miles, 36 mph for 24 miles, and 48 mph for 16 miles. what is its average speed? ( show work)

Solution

Total miles driven: 20+24+16 = 60 miles
.
To calculate the \"time\" driven, you must use the distance formula for each leg.
d = rt
solving for t:
t = d/r
where
t is time
d is distance
r is rate
.
1st leg:
t = d/r = 20/40 = 1/2 hours
2nd leg:
t = d/r = 24/36 = 2/3 hour
3rd leg:
t = d/r = 16/48 = 1/3 hour
.
total time = 1.5 hours
.
Avg speed = \"total distance\"/\"total time\"
Avg speed = 60/1.5 = 40 mph