SOLUTION: Ricardo runs 10 miles each Saturday. If he doubles his usual speed, he can run the 10 miles in one hour less than his usual time. What is his usual speed?

Question 915718: Ricardo runs 10 miles each Saturday. If he doubles his usual speed, he can run the 10 miles in one hour less than his usual time. What is his usual speed?
Answer by Hawksfan(61) (Show Source): You can put this solution on YOUR website!
In this problem you will need to start with equations.
Lets start with the equations:
The basic formula we are using is Distance = Rate* Time or D=R*T
The First sentence tells us that the distance is 10. So the first equation by this sentence is 10 = RT.
The second sentence tells us about the second equation. The Rate is doubled.
We represent that by 2R instead of R. It also says that the time is one hour less represented by T-1. The second equation would then be
10 = 2R * (T-1)
Since both Equations have are equal to 10, we can set them equal to each other. Normally we would have to do either use substitution or elimination with the equations.
RT = 2R(T-1)
RT/R = 2R(T-1)/R
T = 2(T-1)
T = 2T-2
T = 2
10= RT
R = 5

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