SOLUTION: Jack travels from A to B at 30 mph, and returns at 10 mph. Jill leaves at the same time as Jack, and travels from A to B and back at a constant speed of 20 mph. Who gets back first

Question 487869: Jack travels from A to B at 30 mph, and returns at 10 mph. Jill leaves at the same time as Jack, and travels from A to B and back at a constant speed of 20 mph. Who gets back first?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Jack travels from A to B at 30 mph, and returns at 10 mph.
Jill leaves at the same time as Jack, and travels from A to B and back at a constant speed of 20 mph.
Who gets back first?
:
let d = the one way distance
let a = Jack's average speed for the round trip
:
write a time equation
+ =
Multiply by 30a
da + 3da = 30(2d)
da + 3da = 60d
Simplify divide by d
a + 3a = 60
4a = 60
a =
a = 15 mph av speed, obviously, Jill will get back first

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