Question 941764
A jogger can bike 30 miles in the same time as he can run 10 miles.
 If he can bike 10 miles an hour faster than he can job, how fast can he jog?
:
let s = his jogging speed
then
(s+10) = his biking speed
:
Write a time equation; time = dist/speed
{{{30/((s+10))}}} = {{{10/s}}}
cross multiply
30s = 10(s+10)
30s = 10s + 100
30s - 10s = 100
20s = 100
s = 100/20
s = 5 mph is his jogging speed
:
;
Confirm this by finding the time of each
30/15 = 2 hrs running (he runs 10 mph faster than he jogs)
10/5 =  2 hrs jogging