Question 1179938: Justin can run 10 km in the same amount of time that Leo can run 12 km. If Leo can run 1 kph faster than Justin, how fast can Leo run? Found 2 solutions by ankor@dixie-net.com, MathTherapy:Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website! Let J = Justin's speed in km/hr
let L = Leo's speed
:
Justin can run 10 km in the same amount of time that Leo can run 12 km.
Write a time equation, time = dist/speed
j's time = L's time =
cross multiply
12j = 10L
simpilfy, divide by 2
6j = 5L
:
If Leo can run 1 kph faster than Justin,
L = j + 1
or
j = L - 1
how fast can Leo run?
Replace j with (L-1) in the first equation
6(L-1) = 5L
6L - 6 = 5L
6L - 5L = 6
L = 6 km/h is Leo's speed
:
Let Leo's speed be S
Then Justin's is: S - 1
We then get the following TIME equation: ----- Factoring out GCF, 2, in NUMERATORS
5S = 6S - 6 ----- Cross-multiplying
5S - 6S = - 6
- S = - 6
Leo's speed, or