SOLUTION: If i ride my bike 8 miles and then walk 4 miles it takes me 3hrs. If i walk 1/4 the rate that i ride, how fast did i ride my bike?

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Question 297242: If i ride my bike 8 miles and then walk 4 miles it takes me 3hrs. If i walk 1/4 the rate that i ride, how fast did i ride my bike?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let b = your speed riding your bike
Then, your speed walking is %281%2F4%29%2Ab
In words:
(time spent walking and biking) = (distance biking/biking speed) + (distance walking/walking speed)
3+=+8%2Fb+%2B+4%2F%28%281%2F4%29%2Ab%29
Multiply both sides by %281%2F4%29%2Ab
%283%2F4%29%2Ab+=+2+%2B+4
3b+=+4%2A6
b+=+8
The speed biking is 8 mi/hr
check:
3+=+8%2Fb+%2B+4%2F%28%281%2F4%29%2Ab%29
3+=+8%2F8+%2B+4%2F%28%281%2F4%29%2A8%29
3+=+1+%2B+4%2F2
3+=+3
OK