SOLUTION: a man drove a distance of 400km.on return journey he drove 10km per hour slower and took two hours more.what was his speed on outward journey

Question 745613: a man drove a distance of 400km.on return journey he drove 10km per hour slower and took two hours more.what was his speed on outward journey

Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
a man drove a distance of 400km.
on return journey he drove 10km per hour slower and took two hours more.
what was his speed on outward journey
:
Let s = original speed
then
(s-10) = return speed
:
Write time equation; time = dist/speed
:
return time - outbound time = 2 hrs
+ = 2 hrs
mult by s(s-10), resulting in
400s - 400(s-10) = 2s(s-10)
400s - 400s + 4000 = 2s^2 - 20s
Combine as a quadratic equation
2s^2 - 20ts- 4000 = 0
simplify, divide by 2
s^2 - 10s -2000 = 0
Factors to
(s-50)(s+40) = 0
the positive solution is all we want here
s = 50 km/h on the outbound journey
:
:
Check this by finding the time each way
400/40 = 10 hrs return time
400/50 = 8 hrs
---------------
differs by 2 hrs

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