SOLUTION: If one walks 500 feet at 4 miles per hour walking to his/her destination and walks back 500 feet at 3 miles per hour... What is the average speed for the entire trip? How do you ca

Question 263150: If one walks 500 feet at 4 miles per hour walking to his/her destination and walks back 500 feet at 3 miles per hour... What is the average speed for the entire trip? How do you calculate it?
Found 2 solutions by drk, oberobic:
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
Be careful here. Your units are not aligned - -> "500 feet" and "miles" per hour. This is an RTD question. Here is a table based on the given information:
destination . . . . . . . . . . . . . . rate . . . . . . . . . . . . . .time . . . . . . . . . . distance
to. . . . . . . . . . . . . . . . . . . . . . 4*5280 . . . . . . . . . . . . . . . . . . . . . . . . . 500
from. . . . . . . . . . . . . . . . . . . . 3*5280 . . . . . . . . . . . . . . . . . . . . . . . . . .500
average. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1000
we want average speed. This is average rate which is expressed as total distance over total time.
the time for "to" is 500/(4*5280) = .023674242 hrs
the time for "to" is 500/(3*5280) =. 031565656 hrs
so, total time = .055239898 hrs
and total distance is 1000 ft
average speed = 1000/.055239898 ft/hr ~ 18102.8571428 ft / hr
Now you may want the average rate in miles / hr. we get
18102.8571428 ft / hr * 1 mile / 5280 ft ~ 3.42857 mph.
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
We know:
d = rt, where d=distance, r=rate, t=time
d = 500 ft
r = 4 miles per hr (going one way)
r = 3 miles per hr (going the other way)
.
We need to get everything into feet:
4 miles per hr = 4*5280 ft per mile = 21,120 ft per hr
3 miles per hr = 3*5280 ft per mile = 15,840 ft per hr
.
At 4 mph:
500 = 21120 t
t = .02367 hr
.
At 3 mph:
500 = 15840 t
t = .03156 hr
.
The total distance walked: 1000 feet
The total time: .02367 + .03156 = .05523 hrs
1000 = .05523 r
r = 18,106 feet/hr
dividing by 5,280 feet/mile we have
r = 4.329 miles per hr, which is the average rate
.
done.
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