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Mark Keaton's workout consists of jogging for 3 miles and then riding his bike for 5 miles at a speed 4 miles per hour faster
than he jogs. if his total workout time is 1 hour find out his total jogging and biking speed.
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Let J be his jogging speed, in miles per hour.
Then the biking speed is (J+4) mph, according to the condition.
Jogging time is hours; biking time is hours; total time is 1 hour.
It gives the "time" equation
+ = 1.
To solve it, multiply both side by J*(J+4).
3*(J+4) + 5J = J*(J+4)
3J + 12 + 5J = J^2 + 4J
J^2 - 4J - 12 = 0
(J-6)*(J+2) = 0.
Only positive root J = 6 is meaningful.
Answer. Jogging speed is 6 miles per hour. Biking speed is (6+4) = 10 miles per hour.
CHECK. + = = = 1 hour. ! Correct !
Solved.