Question 716205: on a round-trip over the same roads, a car averaged 25 mph going and 30 mph returning. If the entire trip took 5.5 hours, what is the distance each way?
My question is how can you solve how much time it took for each half of the trip?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! on a round-trip over the same roads, a car averaged 25 mph going and 30 mph returning. If the entire trip took 5.5 hours, what is the distance each way?
My question is how can you solve how much time it took for each half of the trip?
---------------
The problem doesn't ask for that, it asks for the distance.
-----
find the avg speed:
avg speed = 2*25*30/(25+30) mi/hr
= 300/11 mi/hr
---
Then d = r*t = (300/11)*5.5 = 150 miles round trip
--> 75 miles each way.
----------------------------------
Check:
75/25 + 75/30 = 3 + 2.5 hours
= 5.5 hours
===================
Avg speed for a round trip is 2*r1*r2/(r1+r2) regardless of the distance
You can call the distance d and work out the eqn.
================================================
Another approach:
The time spent at each speed is inversely proportional to the speed but the ratio is the same as the 2 speeds.
25x + 30x = 5.5
55x = 5.5
x = 0.1
--> 2.5 hours at the faster speed, 3.0 hours at the slower speed.
|
|
|
