SOLUTION: Joe drove at the speed of 45 miles per hour for a certain distance. He then drove at the speed of 55 miles per hour for the same distance. What is the average speed for the whole t

Question 553934: Joe drove at the speed of 45 miles per hour for a certain distance. He then drove at the speed of 55 miles per hour for the same distance. What is the average speed for the whole trip?

Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Joe drove at the speed of 45 miles per hour for a certain distance.
He then drove at the speed of 55 miles per hour for the same distance.
What is the average speed for the whole trip?
:
Let d = distance driven at each speed
then
2d = distance of the whole trip
:
let a = the average speed for the whole trip
:
Write a time equation; time = dist/speed
:
45mph time + 55mph time = total time
+ =
Multiply by the LCM of 45 and 55, 495a
495a* + 495a* = 495a
cancel the denominators;
11ad + 9ad = 495(2d)
20ad = 990d
divide both sides by d
20a = 990
a = 990/20
a = 49.5 mph is the average speed for the trip
:
;
:
Let's check this out, using an assigned distance of 200 mi
+ =
2.22 + 1.82 = 4.04
4.04 = 4.04; confirms our average speed of 49.5 mph
RELATED QUESTIONS
2. Joe drove at the speed of 45 miles per hour for a certain distance. He then drove at... (answered by Alan3354)

Mr. Hoffman drove from Indianapolis to Atlanta on business. The distance between the... (answered by ikleyn)

Question 3.3. Tran drove his car at a constant speed of 55 miles per hour. Which is an (answered by JulietG)

Peter drove at a speed of 60 miles per hour for 2.5 hours. Find the distance traveled... (answered by luke94)

Greg drove at a constant speed in a rainstorm for 280 miles. He took a break, and the... (answered by richwmiller)

greg drove at a constant speed in a rainstorm for 252 miles. he took a break, and the... (answered by josgarithmetic,josmiceli)

Greg drove at a constant speed in a rainstorm for 266 miles. He took a break, and the... (answered by josgarithmetic,MathTherapy)

Greg drove at a constant speed in a rainstorm for 273 miles. He took a break,... (answered by josmiceli)

Greg drove at a constant speed in a rainstorm for 252 miles. He took a break, and (answered by josgarithmetic)