Two RSM students are standing 20ft apart and spot Mrs Rifkin. If they immediately run opposite direction with speeds of 300 ft/min and 200 ft/min, how many hours will pass until they are 3,000 ft apart?

Answer 1

They would be separating at 500 ft/min
time to go 3000 ft at that speed
= 3000/500 min
or
= 6 minutes

or

time taken --- x minutes
distance of one student = 300x
distance of other student = 200x
300x + 200x = 3000
500x = 3000
x = 6 , just like above.

Answer 2

Their combined speeds are 500 meters per minute, but they're 20 feet apart first, so you should multiply 500 by 5 and add 20 (because it's the distance they are apart from each other before they spot Mrs. Rifkin)
5*500+20=2520 (Note: if you did 6 times 500, then it would be 3000, and that's over 3000 if you add the original 20)
So now, subtract 2520 from 3000.
3000-2520=480
Now figure out how much time it takes them to go 480 meters then add the time (in MINUTES!) to 5 minutes because that's how we got 2500 meters.
Your answer should be 5 and ___ minutes.
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