SOLUTION: You can travel 40 mi on your motorbike in the same time it takes your friend to travel 15 mi on his bicycle. If your friend rides his bike 20 mi/h slower than you ride your motorbi

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Question 738657: You can travel 40 mi on your motorbike in the same time it takes your friend to travel 15 mi on his bicycle. If your friend rides his bike 20 mi/h slower than you ride your motorbike, find the speed for each bike.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = speed for motorbike in mi/hr
+s+-+20+ = speed for bikein mi/hrLet +t+ = the time for both in hrs
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Equation for motorbike:
(1) +40+=+s%2At+
Equation for bike:
(2) +15+=+%28+s-20+%29%2At+
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(2) +15+=+s%2At+-+20t+
Substitute (1) into (2)
(2) +15+=+40+-+20t+
(2) +20t+=+25+
(2) +t+=+5%2F4+
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(1) +s+=+40%2Ft+
(1) +s+=+40%2F%28+5%2F4+%29+
(1) +s+=+160%2F5+
(1) +s+=+32+
+s+-+20+=+12+
The motorbike travels at 32 mi/hr
The bike travels at 12 mi/hr
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check:
(2) +15+=+s%2At+-+20t+
(2) +15+=+32%2A%285%2F4%29+-+20%2A%285%2F4%29+
(2) +15+=+40+-+25+
(2) +15+=+15+
OK