SOLUTION: if the speed limit is decreased by 10 km/h on a 100 km stretch of a highway, the trip will take a half hour longer than usual. what is the usual speed limit
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Question 1015582: if the speed limit is decreased by 10 km/h on a 100 km stretch of a highway, the trip will take a half hour longer than usual. what is the usual speed limit Found 2 solutions by josgarithmetic, MathTherapy:Answer by josgarithmetic(39626) (Show Source):
You can put this solution on YOUR website! How long does the trip take USUALLY? t.
How long does trip take at the new speed limit? t+1/2.
Usual r t 100
New Limit r-10 t+1/2 100
RT=D travel rate rule.
Do you know what to do?
(1) Form a system of equations
(2) Solve the system for r and t.
You can put this solution on YOUR website! if the speed limit is decreased by 10 km/h on a 100 km stretch of a highway, the trip will take a half hour longer than usual. what is the usual speed limit
Let usual speed limit be S
Then time taken at usual speed =
Decreasing the speed makes the new speed, S – 10
Time taken at new speed:
We then get:
100(2)(S – 10) = 100(2S) – S(S – 10) ------- Multiplying by LCD, 2S(S – 10)
(S - 50)(S + 40) = 0
S, or original speed limit =
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