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two gears work together. There are 32 teeth on one gear and 36 on the other gear. The first gear makes 128 revolutions per second. How often, during a 24 hour period, will the same two teeth from each gear be together?

 Jul 22, 2016

Best Answer 

 #4
avatar+128475 
+5

Two gears work together. There are 32 teeth on one gear and 36 on the other gear. The first gear makes 128 revolutions per second. How often, during a 24 hour period, will the same two teeth from each gear be together?

 

I saw geno do something like this one the other day......

 

32 = 2^5

36 = 3^2 * 2^2

 

The least common multiple between 36 and 32  =  3^2 * 2^5    =  288

 

So....... the two teeth are together when the first gear makes 288/32  = 9 revolutions   and the second gear makes 288/36 = 8 revolutions

 

And it takes the first gear 9/128 seconds to make 9 revolutions

 

And there are  60*60*24 = 86400 seconds in  a 24 hour period.......so......

 

In 24 hours.......the same two teeth from both gears will be together

 

86400  / [ 9/128] =  1,228,800   times

 

 

 

cool cool cool

 Jul 22, 2016
 #1
avatar+33616 
+5

lcm(32, 36) = 288

 

revolutions in 24 hours = 128*3600*24

 

number of times same teeth together =  128*3600*24/288 → 38400

 

.

 Jul 22, 2016
 #2
avatar+118609 
0

 

Thanks Alan,

That one had me stumped.   I was looking for some really complicated solution :)

 Jul 22, 2016
 #3
avatar+33616 
0

I hope it's right then!

Alan  Jul 22, 2016
 #4
avatar+128475 
+5
Best Answer

Two gears work together. There are 32 teeth on one gear and 36 on the other gear. The first gear makes 128 revolutions per second. How often, during a 24 hour period, will the same two teeth from each gear be together?

 

I saw geno do something like this one the other day......

 

32 = 2^5

36 = 3^2 * 2^2

 

The least common multiple between 36 and 32  =  3^2 * 2^5    =  288

 

So....... the two teeth are together when the first gear makes 288/32  = 9 revolutions   and the second gear makes 288/36 = 8 revolutions

 

And it takes the first gear 9/128 seconds to make 9 revolutions

 

And there are  60*60*24 = 86400 seconds in  a 24 hour period.......so......

 

In 24 hours.......the same two teeth from both gears will be together

 

86400  / [ 9/128] =  1,228,800   times

 

 

 

cool cool cool

CPhill Jul 22, 2016
 #5
avatar+33616 
+5

I think you are right Chris - I didn't separate teeth from revolutions!

Alan  Jul 22, 2016

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