SOLUTION: Two runners start running at the same time from start/finish line of a 400 meter oval track. One runner runs laps of 1 minute 15 seconds and the other runner runs laps of 1 minute

Question 636112: Two runners start running at the same time from start/finish line of a 400 meter oval track. One runner runs laps of 1 minute 15 seconds and the other runner runs laps of 1 minute 45 seconds. HOw long will it be before the runners cross the start/finish line at the smae time? How many laps will each have run?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Two runners start running at the same time from start/finish line of a 400 meter oval track.
One runner runs laps of 1 minute 15 seconds and the other runner runs laps of 1 minute 45 seconds.
How long will it be before the runners cross the start/finish line at the same time?
How many laps will each have run?
:
Change 1 min 15 min to 75 sec; and 1 min 45 sec to 105 sec
Find least common multiple of 75 and 105 using prime factors
75: 3*5*5
105: 3*5*7
LCM: 3*5*5*7 = 525 sec
which is 525/60 = 8.75 min, which is:
8 min 45 sec when both runners cross the finish line at the same time
then
One runner completes exactly 525/75 = 7 laps
and
Other runner completes exactly 525/105 = 5 laps

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