Parenting

Parentcaster

American math education has changed, 2-digit by 2-digit multiplication.

66 x 22

step 1: write 66 x 2 as 122 with a little 1 over the middle 2
step 2: write 66 x 20 as 1,220 with a little 1 over the first 2
step 3: write final answer as 1,452 by adding up the columns

https://SassyHash.artlu.xyz/download

The Once and Future /arthur /bcbhshow. FOSS at GH:artlu99.

PFP is my Native.fun Print, genart unique hash of wallet txns

was anyone else taught the "rainbow" method in school?

ab x cd

step 1: write down last digit of result of (b x d)
step 2: last digit of (a x d) + (b x c) + {whatever was left over}
step 3: (a x c) + {whatever was left over}

we learned it as a gimmick only

I was taught to write the first intermediate step: 66 x 2 as 132, by going right to left and keeping intermediate values in my head.

Seeing the 122 written down on paper triggered me.

It's not wrong though, especially since: a) always go left to right, b) intermediate calcs are disposable, c) less storage mistakes

Philosopher, dad. Formerly Guidepost Montessori. Web3 curious. https://nf.td/matt

it's the "carry the 1", so instead of writing 132, they write 122 with a little 1 on top of the middle 2. 

they can always work left-to-right, and don't have to remember any numbers in their head

@backpack put a bank in your pocket and use your money whenever, wherever, however without permission

/backpack
/notdevin
icebreaker.xyz/notdevin

same here. are your kids being taught the same in school nowadays?

I learned right to left starting with 1s and then progressing. Less steps slightly worse mental math, never needed anything different  

       66
x     22
     132
+1320
  1452