Tom's home is 1800m from his school. One morning he walked part of the way to school and then ran the rest. If it took him 20 minutes or less to get to school, and he walks at 70 m/min and runs at 210 m/min, how far did he run?
[Sol] If the distance he ran is x m, the distance he walked is ( )m. Therefore,
[Sol] If the distance he ran is x m, the distance he walked is ( )m. Therefore,
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Answer:
let x = distance he ran
then
(1800-x) = distance he walked
:
Write a time equation: time = dist/speed
:
Run time + walk time = 20 min
x%2F210 + %281800-x%29%2F70 = 20
Multiply by 210 to get rid of the denominators, results
x + 3(1800 - x) = 210 * 20
:
x + 5400 - 3x = 4200
x - 3x = 4200 - 5400
-2x = -1200
x = %28-1200%29%2F%28-2%29
x = +600 meters he ran
:
:
Confirm our solution by finding the times
1800 - 600 = 1200 m he walked
walk time: 1200/70 = 17.14 min
run time: 600/210 = 2.86 min
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total travel time: 20 min
Step-by-step explanation:
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