Question 153852
Lisa Chung wants to cover a 6 miles course in 1 hour by running part of the way and walking the rest. She also wants to make a 5 minute stop for water. Lisa runs 8 mph and walks 3 mph. How many miles will she have to run? 
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Let "x" be the miles Lisa runs; Then she will walk "6-x" miles.
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Her running time: distance/rate = x/8 hrs
Her walking time: distance/rate = (6-x)/3 hrs
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EQUATION
run time + walk time + (5/60)water time = 1 hr
x/8 + (6-x)/3 + (5/60) = 1
Multiply thru 120:
15x + 40(6-x) + 10 = 120
15x + 240 - 40x + 10 = 120
25x = 130
x = 5.2 miles (distance she must run)
6-x = 0.8 miles (distance she must walk)
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Cheers,
Stan H.