SOLUTION: Two brothers, Marco and Fernando, are training for a a marathon. Marco runs at a rate of 6 miles per hours. Fernando runs at a rate of 7.2 miles per hour. they start a training run

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Question 1148277: Two brothers, Marco and Fernando, are training for a a marathon. Marco runs at a rate of 6 miles per hours. Fernando runs at a rate of 7.2 miles per hour. they start a training run at the same time in the same direction. In how much time wiil they be 0.3 miles apart?
Found 2 solutions by greenestamps, josmiceli:
Answer by greenestamps(13216) About Me  (Show Source):
You can put this solution on YOUR website!


Just as

distance = rate times time

it is also true that, if the times are the same,

(difference in distances) = (difference in rates) times time

So

time = (difference in distances) / (difference in rates)

time = 0.3/(7.2-6) = 0.3/1.2 = 1/4 (hours)

ANSWER: 1/4 hour, or 15 minutes

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +d+ = the distance the slower one goes
+d+%2B+.3+ = the distance the faster one goes
Let +t+ = the time in hrs for them to go these distances
------------------------
Marco's equation:
(1) +d+=+6t+
Fernando's equation:
(2) +d+%2B+.3+=+7.2t+
---------------------------
Plug (1) into (2)
(2) +6t+%2B+.3+=+7.2t+
(2) +1.2t+=+.3+
(2) +t+=+1%2F4+ hrs
------------------------
In 1/4 hrs, or 15 min, they will be .3 mi apart
------------------------
check:
(1) +d+=+6%2A%281%2F4%29+
(1) +d+=+1.5+ mi
and
(2) +d+%2B+.3+=+7.2%2A%281%2F4%29+
(2) +d+=+1.8+-+.3+
(2) +d+=+1.5+ mi
OK