Why did I fully have to look at this for half an hour to work out what the fuck was going on
only real math dumbasses will understand this right away and thatâs me babey
Iâm fucking screaming
This happened to a kid at work. He sat there for a second, sighed and whispered âdamnâ
Is this new math? Iâm so confused
This is why we have ânew mathâ aka cc. So kids donât grow up getting stuck when thereâs an equation they have difficulty with and they have strategies to help them mentally compute. I once saw a student do an entire page of subtracting from teens like this (I was not the teacher) and itâs honestly sad when parents âteachâ their child the standard algorithm before they have a solid conceptual understanding of subtraction because the standard algorithm doesnât always help!
I stan for common core math and the standards for mathematical practice. So sue me.
im just curious.. how would this problem be solved with ânew mathâ ? what is the process like?
One way itâs solved with â"new mathââ is that kds at a young age are being taught their âdoublesâ so they should have memorized what 1+1, 2+2, 3+3, etc. all the way up to 10+10 is. That alone should be enough for them to know that 18-9=9 because part of knowing your doubles is also knowing that taking one away from the sum leaves you with the same number.
The OTHER method is basically like distribution. Consider that 18-9 can be shifted into an easier problem by just using blocking.
18-10 is an easier problem, right? the answer is clearly 8. but 10 is taking one too many away from 18, so you need to put one back. 18-9 is then 9.
wow thats definitely different from how i learned it growing up.. the other method is kinda similar to how i learned it but the interpretation is different
cause the way i learned it, once you do a problem where a digit goes 8-9 then you reset to 10 when you hit 0 then you subtract further
so 8-9 becomes 8-8 = 0 then that becomes 10 then you subtract another which becomes 10 - 1 = 9
so for lets say 17 - 9
you start from the right, you get 7 - 9 which becomes 7 - 7 = 0 then you subtract 2 more from 10 to get 8 then since youâve regrouped previously, you remove 1 from the next so yeah you end up with 0 and an 8
Also subtraction and addition are opposites of each other (so is multiplication and division). I work with grade school kids and I give them this as an alternative in case they don't understand the initial way that is taught at school. So if you "flip" the equation, and change the minus sign to a plus sign, you end up with _+9=18. Then all you'll have to do is either count from 9 till you get to 18 or remember your doubles (which for some kids, the visual reminder jogs their memory)
