SOLUTION: A train goes one way at a speed of x mph and y mph on the return trip. What is its average speed for the trip.

Question 204073: A train goes one way at a speed of x mph and y mph on the return trip. What is its average speed for the trip.

Found 2 solutions by feliz1965, RAY100:
Answer by feliz1965(151) (Show Source): You can put this solution on YOUR website!
Here is a tip:
Average speed = distance divide by time or A = d/t.
Can you finish now?
If not, look at the link below for extra help.
http://oregonstate.edu/instruct/mth251/cq/Stage2/Lesson/speed.2.html
Answer by RAY100(1637) (Show Source): You can put this solution on YOUR website!
velocity = distance/time,,,or t=d/v
.
,total time = d/x +d/y =(dy+dx)/xy = d(x+y)/xy
.
total distance =2d
.
velocity total = total distance / total time = 2d / {d(x+y)}/xy = 2xy/x+y
.
check,,let x=50, y=60, d=100 (all arbitrary)
.
vel = 2(50)(60) / (50 +60) = 6000/110=54.55 mph
.
BIG NOTE, it is NOT (50 +60) /2 = 55,,,,or (x+y)/2
.
avg vel = distance/time,,,,,,200 / {100/50 +100/60} = 54.55
RELATED QUESTIONS
A freight train averages 30 mph traveling to its destination with full cars and 40 mph on (answered by Alan3354)
`A train goes from New Orleans to Boston at 40 mph. On the way back it returns with a... (answered by josmiceli)
A train goes from New Orleans to Boston at 40 mph. On the way back it returns with a... (answered by Alan3354)
A train travels from Beauford to Fallsville at a speed of 88 mph and then travels back to (answered by Alan3354)
A train travels from Beauford to Fallsville at a speed of 88 mph and then travels back to (answered by Alan3354)
A jet flies from New York to Atlanta at an average rate of 420 mph. On the return trip,... (answered by jim_thompson5910)
a train traveled from one city to another in 5 hours at a speed of 60 mph. on the return... (answered by lenny460)
a car traveled 600 miles at 60 mph and 40mph on the return trip. What was the average... (answered by checkley77)
A train goes from New Orleans to Boston at 40 mph. On the way back it returns with a... (answered by Alan3354)