SOLUTION: a car travels 40 mph for 20 miles, 36 mph for 24 miles, and 48 mph for 16 miles. what is its average speed?

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Question 265478: a car travels 40 mph for 20 miles, 36 mph for 24 miles, and 48 mph for 16 miles. what is its average speed?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
a car travels 40 mph for 20 miles, 36 mph for 24 miles, and 48 mph for 16 miles. what is its average speed?
:
Total distance 20 + 24 + 16 = 60 mi
Let x = average speed for the 60 mi trip
:
Write time equation, time = dist/speed
:
20%2F40 + 24%2F36 + 16%2F48 = 60%2Fx
Multiply equation by 720x, results
18x(20) + 20x(24) + 15x(16) = 720(60)
:
360x + 480x + 240x = 43200
:
1080x = 43200
x = 43200%2F1080
x = 40 mph average speed
:
:
Check solution in the original time equation
20%2F40 + 24%2F36 + 16%2F48 = 60%2F40
.5 + .67 + .33 = 1.5