Problema Solution
Marina can bicycle 19.5 miles in the same time it takes her to run 6 miles. She bikes 9 miles per hour faster than she runs. At what speed does Marina run
Answer provided by our tutors
let
b = the bicycle speed of Marin
r = the running speed of Marina
She bikes 9 miles per hour faster than she runs
b = r + 9
Marina can bicycle 19.5 miles in the same time it takes her to run 6 miles and we will use the formula speed = distance/time => time = distance/speed
19.5/b = 6/r cross multiply
19.5r = 6b
by solving the system of equations
b = r + 9
19.5r = 6b
we find
b = 13 mph
r = 4 mph
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Marina runs at 4 miles per hour.