SOLUTION: Craig Drives 20 miles per hour faster than sara. in the same time that sara drives 225 miles, craig drives 325 miles. find the speed of each car

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Question 206567: Craig Drives 20 miles per hour faster than sara. in the same time that sara drives 225 miles, craig drives 325 miles. find the speed of each car
Found 4 solutions by HyperBrain, ikleyn, josgarithmetic, greenestamps:
Answer by HyperBrain(694) About Me  (Show Source):
You can put this solution on YOUR website!
d=vt so t=d/v
Let x=sara's speed
Then x+20=craig's speed
225/x=325/(x+20)
Multiply both sides by x(x+20)
225(x+20)=325x
225x+4500=325x
100x=4500
x=(Sara's speed) 100 mi/hr
x+20=(Craig's speed) 120 mi/hr
Power up,
HyperBrain!

Answer by ikleyn(53937) About Me  (Show Source):
You can put this solution on YOUR website!
.
Craig Drives 20 miles per hour faster than sara.
in the same time that sara drives 225 miles, craig drives 325 miles. find the speed of each car
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        The answer in the post by @HyperBrain is INCORRECT due to arithmetic error on the way.
        I came to provide a correct solution


d=vt so t=d/v
Let x be the Sara's speed, in miles per hour.
Then the Craig's speed is (x+20) miles per hour.
225/x=325/(x+20)
Multiply both sides by x(x+20)
225(x+20)=325x
225x+4500=325x
100x=4500
x = 45 mi/hr ((Sara' speed)
x+20 = 45 + 20 = 65 mi/hr (Craig' speed).

CHECK the travel time.   225%2F45 = 5 hours.   325%2F65 = 5 hours.     Precisely correct !

Solved correctly.



Answer by josgarithmetic(39835) About Me  (Show Source):
You can put this solution on YOUR website!
               SPEEDS        TIMES            DISTANCES

Craig           r+20         325/(r+20)         325

Sara             r           225/r              225

The two time quantities described as equal.
325%2F%28r%2B20%29=225%2Fr.
Solve for r.

Answer by greenestamps(13364) About Me  (Show Source):
You can put this solution on YOUR website!


A quick mental solution....

The difference in distances is 100 miles; the difference in speeds is 20 mph.
Therefore the amount of time is 100/20 = 5 hours.
Therefore Craig's speed is 325/5 = 65 mph and Sara's speed is 225/5 = 45 mph.

ANSWERS:
Craig 65 mph
Sara 45 mph