SOLUTION: David and Andrew are traveling to a Mathematics conference. David travels 110 miles in the same time that Andrew travels 140 miles. Andrew travels 15 miles per hour faster than

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Question 1160242: David and Andrew are traveling to a Mathematics conference. David travels 110 miles in
the same time that Andrew travels 140 miles. Andrew travels 15 miles per hour faster
than David. Find the average rate of each person.
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Found 3 solutions by Alan3354, greenestamps, josgarithmetic:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
David and Andrew are traveling to a Mathematics conference. David travels 110 miles in
the same time that Andrew travels 140 miles. Andrew travels 15 miles per hour faster
than David. Find the average rate of each person.
======================================
d = r*t
The times are the same.
----------------
t = d/r
t = 110/r = 140/(r+15)
---
Cross multiply
110(r+15) = 140r
110r + 1650 = 140r
1650 = 30r
r = 55
etc
Answer by greenestamps(13203)   (Show Source): You can put this solution on YOUR website!


The difference in distances is 140-110=30 miles; the difference in rates is 15mph.

That means the time in hours is 30/15 = 2.

That in turn means David's rate is 110/2 = 55mph and Andrew's rate is 140/2 = 70mph.
Answer by josgarithmetic(39623)   (Show Source): You can put this solution on YOUR website!
          SPEED    TIME        DISTANCE

David      r       110/r        110

Andrew    r+15     140/(r+15)   140

The time quantities were given as equal.
-----------simplify and solve for r.
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