SOLUTION: A bus and a car traveled a distance of 140km from town A to town B. The car left town A 45 minutes after the bus, but it reached town B 15 minutes earlier than the bus. If the aver

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A bus and a car traveled a distance of 140km from town A to town B. The car left town A 45 minutes after the bus, but it reached town B 15 minutes earlier than the bus. If the aver      Log On

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Question 1053620: A bus and a car traveled a distance of 140km from town A to town B. The car left town A 45 minutes after the bus, but it reached town B 15 minutes earlier than the bus. If the average speed of the bus was 60 km/hr what was the average speed of the car?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = the average speed of the car in km/hr
Let +t+ = the time in hrs the car takes to get to town B
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How far did the bus get in the 1st 45 min?
+d%5B1%5D+=+60%2A%283%2F4%29+
+d%5B1%5D+=+45+ km
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Start a stop watch when the car leaves town A
Let +t+ = time in hrs on stop watch when car
gets to town B
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Equation for the car:
(1) +140+=+s%2At+
Equation for the bus:
(2) +140+-+45+=+60%2A%28+t+%2B+1%2F4+%29+
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(2) +95+=+60t+%2B+15+
(2) +60t+=+80+
(2) +t+=+4%2F3+
and
(1) +140+=+s%2At+
(1) +140+=+s%2A%284%2F3%29+
(1) +s+=+%283%2F4%29%2A140+
(1) +s+=+105+
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The average speed of the car is 105 km/hr
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check answer:
The total time for the bus is:
+3%2F4+%2B+%28+4%2F3+%2B+1%2F4+%29+
+9%2F12+%2B+16%2F12+%2B+3%2F12+=+28%2F12+
+28%2F12+=+7%2F3+
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The bus travels +140+ km for +7%2F3+ hrs
+140+=+60%2A%287%2F3%29+
+420+=+60%2A7+
+420+=+420+
OK