First the forum says 4th grade, but the books are not titled by grade, so is 4A equivalent to 4th grade? Why is the forum titled by grade if the books are not?
My question is regarding unit 2 enrichment 1 mental math multiplication and division (pg 36).
First, what is the point of this? If one is going to write down a number and remember the ones place to essentially carry it over (left to right) why wouldn't we just use this same method going right to left, remembering the tens place as you move over? Essentially working the same as you would normally just remembering the carried number to add to the next place column?
For instance, in the example given 5276 x 3 why not say 6*3 write 8 remember 1 then 7*3 add 1 to 1 in one's place write down 2 remember tens place (2) 2*3 add the 2 write 8 and so on. Essentially how you've already learned to compute it, just remembering the number carried?
I am not trying to difficult, just trying to figure out the purpose of this version of mental math. It seems to complicate things.
Additionally it tells me to use mental math 9 for examples to do with the student! The last problem 2624*8 does not work with this system because on the second step, remembering 6 then adding it to 4 from the 6*8=48 gives us 10 which means you have to go back left to add it to the 1 in the ten thousands place for 20,000! This was not explained in the lesson and created a lot of angst in my son who was doing these fine and then got to this one which changed the scenario. Working right to left as I suggest above would ameliorate this!
While I love MM, this seems very complicated and counterintuitive!
Welcome any comments!