SOLUTION: kristin is 20 miles behind a truck that is driving 50 miles per hour. how long will it take her to catch up to the truck? how far will she go in that time?

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Question 874082: kristin is 20 miles behind a truck that is driving 50 miles per hour. how long will it take her to catch up to the truck? how far will she go in that time?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
r = Kristin's speed and r%3E50. Her speed was not given but the order relation was implied. She will go 20 miles more than the truck to catchup.


_______________speed_________time_________distance
Kristin________r_____________t____________d+20
Truck__________50____________t____________d

The unknown variables for which to solve are t and d. We must expect r is some constant rate, but this value was not given.

These equations are what the data allow for us:
highlight_green%28rt=d%2B20%29 and highlight_green%2850t=d%29.

rt-20=d;
Substituting,
50t=d
50t=rt-20
50t-rt=-20
rt-50t=20
t%28r-50%29=20
highlight%28t=20%2F%28r-50%29%29 HOURS.

Again either equation, here choosing the truck,
d=50t
d=50%2820%2F%28r-50%29%29
highlight%28d=100%2F%28r-50%29%29 MILES movement of the truck.
This means 20%2B100%2F%28r-50%29 miles movement for Kristin.

If you knew r for Kristin, then you can find values for t and d.