Homework Help Forum: 5th Grade Math

Posted by Sally on Thursday, November 5, 2009 at 11:45pm.

Nick and Isaiah both run a mile. Nick runs in 8 minutes and Isaiah runs it in 10 minutes. How long would it take Nick to run pass Isaiah for a second time. I think the answer is 16 mintues. The LCM =40

• 5th Grade Math - Angela pickens, Thursday, November 5, 2009 at 11:49pm

  How did you get that first of all?

  
  

• 5th Grade Math - Sally, Thursday, November 5, 2009 at 11:56pm

  The chapter was about finding the LCM which in this case is 40. But I thought since the first time around it takes him 8 minutes, then the 2nd time would be 16 minutes. It would take him 5 trips to equal 40 and Isaiah 4 trips. But Nick's time is still beter than Isaiah.

  
  

• 5th Grade Math - Sally, Thursday, November 5, 2009 at 11:58pm

  Oh by the way they start at the same time..

  
  

• 5th Grade Math - Reiny, Friday, November 6, 2009 at 8:06am

  Nick's rate is 1/8 mi/min Isah's rate is 1/10 mi/min (Time = Distance/rate or Distance = rate x time) You don't say how long the track is, but we know that if Nick ran n laps, at the first time Isah is passed, Isah would have run n+1 laps So Nick's time = (n+1)/(1/8) minutes Isah's time = n/(1/10) minutes. At the times would be the same for the first passing, so (n+1)/(1/8) = n/(1/10) This solves to n = 4 subbing that back into either of their times gives me 40 minutes. So Nick will pass Isah for the first time in 40 minutes, and the second time obviously in 80 minutes. (clearly they must be running some type of marathon)

  
  

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