college math
posted by Lorie .
It takes Mike 8 minutes to walk to the store from his house. The return trip takes 13 minutes because he walks 1mph slower due to the bags he is carrying. How fast did Mike walk on his way to the store? Carry out one decimal place.
Thanks in advance!

rate going to store  x mph
rate coming back  x1 mph
(8/60)x = (13/60)(x1)
times 60
8x = 13(x1)
8x  13x = 13
5x = 13
x = 2.6
So he walked to the store at 2.6 mph
check:
(8/60)(2.6) = .34666...
(13/60)(1.6) = .34666... , > same distance 
distance = speed*time, and the two distances are the same, so
8s = 13(s1)
s = 13/5 = 2.6 mph
Note that we can mix minutes and mph, because the same factor would be applied to both sides if we converted everything to minutes or hours. As long as the units on both sides match, we are ok.