# Does it Hertz?

I am in a training class this week for turbine operations and maintenance. My teacher introduced a question by saying we would use a certain gearbox, which makes the math easy.
The (mostly rhetorical) question was:

A gear is spinning at 250 Hertz and it has 12 gear teeth.  When multiplying those together, what is the speed of each gear tooth?

Within seconds, I said 3,000 Hertz and my other 5 classmates looked at me shocked (including the 2 engineers).  I’m not sure if it was the introduction that the math would be made “easy” by the numbers he chose, or if I was looking at the numbers differently since I helped my friend factor some polynomials over the weekend.  Regardless, let me tell you how I did it.

Unlike most, when I see the number 25 I get excited because it reminds me of quarters, which was the first numbers I learned – Money \$\$.  Just after learning your multiples of 0, 1, 2, 5, 10, 11, all Algebrains (I just made that up) should learn your multiples of 25.  With 25, the way I think about it is “It takes four of these to total 100.”  So when multiplying 25 times 12, we have three-100s.  But since we had 250 and not just 25, we now have thirty-100s also known as 30,00 or 3 thousand!

P.S. what we were really calculating in the class is known as the Gear Mesh Frequency, which I had to research the exact term for you all and myself :)