<PRE><B>Question 274343</B>
 running one training segment at 8 kilometers per hour and then a second at 10 kilometers per hour.
 If the total running time is 3.5 hours and the total distance is 31 kilometers, how long should he run at each speed?
:
Let t = time running at 10 km/hr
then
(3.5 - t) = time running at 8 km/hr 
:
Write distance equation: dist = speed * time
:
8 km dist + 10 km dist = 31 km
8(3.5-t) + 10t = 31
28 - 8t + 10t = 31
2t = 31 - 28
2t = 3
t = 1.5 hr at 10 km/hr
and
3.5 - 1.5 = 2 hr at 8 km/hr
:
:
Check solution by finding the total dist
8(2) + 10(1.5) =
16 + 15 = 31</PRE>