SOLUTION: A jogger ran 9 miles in an hour. For the last 4 miles he jogged 2 mph slower than he did for the first 5 miles. How fast did he jog for the first 5 miles?

Question 607449: A jogger ran 9 miles in an hour. For the last 4 miles he jogged 2 mph slower than he did for the first 5 miles. How fast did he jog for the first 5 miles?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
I misunderstood this problem, sorry!
let s = his speed the first 5 mi
then
(s-2) = his speed the last 4 mi
:
Write a time equation; time = dist/speed
:
+ = 1
multiply by s(s-2), results
5(s-2) + 4s = s(s-2)
:
5s - 10 + 4s = s^2 - 2s
9s - 10 = s^2 - 2s
0 = s^2 - 2s - 9s + 10
A quadratic equation
s^2 - 11s + 10 = 0
Factors to
(s-1)(s-10) = 0
two solutions
s = 1
and
s = 10 mph is the only reasonable answer for the first 5 miles
:
:
See if this checks out, find the times
5/10 + 4/8 = 1
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