Posted by **Danessa** on Tuesday, September 25, 2007 at 5:29pm.

One model train travels around a loop every 5 minutes. The other travels on anothe loop every 4 minutes. If they begin at the same point at the same time, how much time will pass before they meet at that point again?

- Math -
**bobpursley**, Tuesday, September 25, 2007 at 5:40pm
The rate for the first is one loop per 5min, the other one loop per four minutes. The combined rate is the sum of these:

1loop= (lloop/5min + 1loop/4min)*time

time= 1/(1/5 + 1/4) minutes

This is somewhat tricky to get combined, if you wish, you can make decimas..

time= 1/(.2+.25)= 1/.45 and you take it from there.

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**bobpursley**, Tuesday, September 25, 2007 at 6:15pm
time= 1/.45= 2.2 seconds.

- Math -
**bobpursley**, Tuesday, September 25, 2007 at 6:16pm
oops..time= 2.2 minutes.

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