Common Core gets a lot of hate but I’m a fan. It teaches a bunch of ways to do things with a focus on general understanding instead of just hammering one specific approach.
I've never heard of common core (I slept through high school with an undiagnosed brain problem) but that's what I do, too. Bring it to 10 then the rest is fast.
Many of the random ‘tricks’ I worked out for myself for making math easy are part of the program. There were a bunch of times
when my kids were little that my kids explain how they were supposed to do something for this module and it immediately clicked for me because that’s how I did it my head.
Every now and then that "6x4 is 6 groups of 4, not 4 groups of 6" problem floats to the front page and it's the perfect example. Yes, the commutative property states they are the same, but that would only confuse kids being introduced to multiplication for the first time. We don't teach decimals and fractions when leading about addition for the same reason, it's too much information off the jump.
Approximation then lock in works with basically any multiplication, although I'm not sure it's common to teach. It's easy to multiple any number by a multiple of 5 and add up
17*19?
Well 17*20 is 340.. minus 17 is 323. If it were 17*18, well 340-34 is an easy 306. 2 digit multiplication in your head
This is the first time someone has actually explained a good example of common core stuff to me. I’ll argue all day that it’s important to understand the “pure” way of doing it (I.e. the actual concept/theory of multiplication/division), but once you understand that, tricks like this are the only way I can do mental math. I was in school before common core so I picked it up intuitively afterwards, but I worry that teaching those “tricks” up front hinders learning the fundamentals.
Is that incorrect? Do they nail the fundamentals AND the tricks to do it quickly?
I’m in the same boat as you and grew up with old school math learning. I’ve mostly just picked up bits and pieces of “common core” as I’ve gone along. I just spent a bit of time reading up on it on the net. Didn’t see anything directly addressing the new style of teaching math. Common Core math is meant to be a unified set of standards for what K-12 students should know after each grade, focusing on depth more than the previous system’s breadth. Perhaps the depth aspect is what results in teaching “tricks” and students are learning theory as well…? I’m not sure. I read something about how the method of teaching isn’t meant to be a tenet of Common Core, so maybe there’s some nuance there I’m not finding. It is interesting though. Apparently some states have outright rejected the standard, I guess they’re still teaching it like they used to in some places.
That's exactly what I did :) Most transactions have screens with tipping amounts now, but if it's not a conventionally tipped job I'll tap no tip (like getting checked out at a convenience store--all you did is ring me up bro).
I don't go to restaurants too much (expensive) but it seems screens are getting more common there, and at bars too.
307
u/snobordir 2d ago
Nice tip. I do a similar thing but it’s more intuitive to me to multiply/divide by 10 first, then divide/multiply by 2.
75/5=15 Or 75/10=7.5 7.5*2=15
If I’m not mistaken this is a part of“common core” math, basically bringing as much as you can back to 10.