When I first came beyond the ladder method (ie: the upside-down cake method) for finding greatest common factors and everyman mutual multiples, I thought it was zilch brusk of complete genius. This was pretty recent, too! I beloved learning new methods for teaching math concepts. Prime number factoring is super cool and extremely useful in building number sense, but if the goal is to find GCF and specially LCM, this cake method makes the process so much easier.Here is a simple video explaining the procedure:
On the outside of the upside down cake are all the factors the two numbers take in common. On the bottom are the "leftover" numbers.
The GCF is the product of all the common factors on the left. The LCM is the product of the GCF and the "leftovers" on the bottom.
I wanted to brand a math word wall reference for this method that students could refer to whenever they are finding GCF, LCM or fifty-fifty simplifying fractions (another swell use for this method brought up in our Visual MathFacebook group).You can get the GCF & LCM word wall references free in my math resource library. This math word wall reference is also part of my 6th grade math discussion wall.
For practise, I made this set up of self-checking GCF & LCM solve 'n check task cards. Students discover GCF and LCM on the card then add, subtract, multiply or carve up their answers and compare against the check number. Changes are if the numbers match, GCF and LCM were constitute correctly.
And a new GCF and LCM digital math escape room.
Another absurd give-and-take that came up in the FB group was near relative prime numbers. In the word wall reference above, LCM= 2x2x2x3x10. While 10 is non prime number, it is relatively prime because it and three have no more factors in common.
And so nosotros accept the block method for finding GCF and LCM and we have skillful sometime prime factoring. Any other methods?
When I was in grad school we learned near the Euclidean algorithm for finding GCF. Above is an example of how this algorithm works for finding that the GCF of 81 and 57 is 3.
I even so like the cake method better :)
I made this GCF, LCM and Prime Factors math pennant before learning nigh the cake method. It was that recent! I think using the cake method would be a bully way to consummate the problems on the pennants.
Y'all may say I'm a touch obsessed with prime number numbers. We learned how they are used in PIN codes and other super cool spy stuff in grad school (though I just remember shadows of all this now).
What has stuck with me is that every number has its own, unique "prime fingerprint". No two numbers share the aforementioned cord of factors. Super cool.
It seems so obvious now, but when I realized this, numbers started feeling a lot like building blocks, almost like chemical elements.
A few months ago I added this prime factorization reference to my 4th class math word wall. I as well pulled these pieces out for my blog (you can get them equally part of my costless math resource library).
How exercise you teach finding GCF and LCM? Practice you have kids prime factor or do you use the cake method? Something else?
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