SOLUTION: A salesman drives from Ajax to Barrington, a distance of 133 mi, at a steady speed. He then increases his speed by 14 mi/h to drive the 168 mi from Barrington to Collins. If the se

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Question 1107231: A salesman drives from Ajax to Barrington, a distance of 133 mi, at a steady speed. He then increases his speed by 14 mi/h to drive the 168 mi from Barrington to Collins. If the second leg of his trip took 7 min more time than the first leg, how fast was he driving between Ajax and Barrington?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
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                 SPEED       TIME            DISTANCE

A to B            r          133/r            133

B to C           r+14        168/(r+14)       168

DIFFERENCE                    7/60


highlight_green%28168%2F%28r%2B14%29-133%2Fr=7%2F60%29
Simplify and solve this equation.
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24%2F%28r%2B14%29-19%2Fr=1%2F60
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24r-19%28r%2B14%29=%28r%5E2%2B14r%29%2F60

24%2A60r-19%2A60%28r%2B14%29=r%5E2%2B14r
1440r-1140r-15960=r%5E2%2B14r
300r-15960=r%5E2%2B14r
r%5E2-286r%2B15960=0

discriminant,... 17956
discriminant, 17956=134%5E2
(286^2-4*15960=81796-63840=17956)


r=%28286%2B-+134%29%2F2


first part of trip: system%28highlight%28r=76%29%2C+OR%2C+highlight%28r=210%29%29