SOLUTION: Brenda and her husband Randy bicycled cross-country together.One morning,Brenda rode 30 miles.By traveling only 5 miles per hour faster and putting in one more hour,Randy covered t

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: Brenda and her husband Randy bicycled cross-country together.One morning,Brenda rode 30 miles.By traveling only 5 miles per hour faster and putting in one more hour,Randy covered t      Log On

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Question 171699: Brenda and her husband Randy bicycled cross-country together.One morning,Brenda rode 30 miles.By traveling only 5 miles per hour faster and putting in one more hour,Randy covered twice the distance.Brenda covered.What was the speed of each cyclist?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
d+=+r%2At for both of them
For Brenda:
(1) d%5Bb%5D+=+r%5Bb%5D%2At%5Bb%5D
For Randy:
(2) d%5Br%5D+=+r%5Br%5D%2At%5Br%5D
-------------
Given is:
d%5Bb%5D+=+30
d%5Br%5D+=+60
r%5Br%5D+=+r%5Bb%5D+%2B+5
t%5Br%5D+=+t%5Bb%5D+%2B+1
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Now I can rewrite (1) and (2)
(1) 30+=+r%5Bb%5D%2At%7Bb%5D
t%5Bb%5D+=+30%2Fr%5Bb%5D
(2) 60+=+%28r%5Bb%5D+%2B+5%29%2A%28t%5Bb%5D+%2B+1%29
(2) 60+=+%28r%5Bb%5D+%2B+5%29%28%2830%2Fr%5Bb%5D%29+%2B+1%29
(2) 60+=+30+%2B+150%2Fr%5Bb%5D+%2B+r%5Bb%5D+%2B+5
Multiply both sides by r%5Bb%5D
(2) 60r%5Bb%5D+=+35r%5Bb%5D+%2B+150+%2B+r%5Bb%5D%5E2
(2) r%5Bb%5D%5E2+-+25r%5Bb%5D+%2B+150+=+0
Looking at this, I see %28-15%29%2A%28-10%29+=+150 and -10+-15+=+-25
(2) %28r%5Bb%5D+-+15%29%28r%5Bb%5D+-+10%29+=+0
This is true if either r%5Bb%5D+=+10 or r%5Bb%5D+=+15
If r%5Bb%5D+=+10, then
r%5Br%5D+=+r%5Bb%5D+%2B+5
r%5Br%5D+=+10+%2B+5
r%5Br%5D+=+15
---------------
t%5Bb%5D+=+30%2Fr%5Bb%5D
t%5Bb%5D+=+30%2F10
t%5Bb%5D+=+3
---------------
t%5Br%5D+=+t%5Bb%5D+%2B+1
t%5Br%5D+=+3+%2B+1
t%5Br%5D+=+4
---------------
Putting this together,
For Brenda:
(1) 30+=+10%2A3
For Randy:
(2) 60+=+15%2A4
---------------
These answers work, but what if r%5Bb%5D+=+15?
t%5Bb%5D+=+30%2Fr%5Bb%5D
t%5Bb%5D+=+30%2F15
t%5Bb%5D+=+2
-----------------
r%5Br%5D+=+r%5Bb%5D+%2B+5
r%5Br%5D+=+15+%2B+5
r%5Br%5D+=+20
-----------------
t%5Br%5D+=+t%5Bb%5D+%2B+1
t%5Br%5D+=+2+%2B+1
t%5Br%5D+=+3
-----------------
Putting these together,
(1) 30+=+15%2A2
For Randy:
(2) 60+=+20%2A3
These answers work too, so
The speeds of the cyclists were either
(1) Brenda went 10 mi/hr and Randy went 15 mi/hr
(2) Brenda went 15 mi/hr and Randy went 20 mi/hr