SOLUTION: harry stopped the car at the main entrance.here we are,exactly seven minutes late.he said this time i avereged 30 miles per hour.last time we did the trip we were five minutes ear

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Question 724285: harry stopped the car at the main entrance.here we are,exactly seven minutes late.he said this time i avereged 30 miles per hour.last time we did the trip we were five minutes early.and we sarted at the same time this time i avereged 36 miles per hour. what was the distance?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Here we are, exactly seven minutes late. This time I averaged 30 miles per hour.
Last time we did the trip, we were five minutes early.
We started at the same time. This time I averaged 36 miles per hour.
What was the distance?
:
Since we are using mph:
Change 5 min to 5/60 hr
Change 7 min to 7/60 hr
:
let t = normal "on-time" time for the trip
:
Write a distance equation, dist = speed * time,
36(t-5%2F60) = 30(t+7%2F60)
divide both sides by 6
6(t-5%2F60) = 5(t+7%2F60)
6t - 30%2F60 = 5t + 35%2F60
reduce the fractions
6t - 6%2F12 = 5t + 7%2F12
6t - 5t = 7%2F12 + 6%2F12
t = 13%2F12 hr is the normal travel time
:
Find the distance when 7min late, 67 min
d = 30 * [13%2F12%29 + 7%2F60]
d = 30 * [65%2F60%29 + 7%2F60]
d = 30 * 72%2F60
d = 72%2F2
d = 36 miles
:
Check the distance when 5 min early
d = 36 * [65%2F60 - 5%2F60]
d = 36 * 60%2F60
d = 36 miles,