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dem4decades

(11,282 posts)
1. Relax, I can remember my wife's home phone number from 1974 but can't remember her cell number.
Fri Jan 1, 2021, 07:17 PM
Jan 2021

Some stuff you don't use just goes by the wayside, the important things you remember. Every phone has a calculator and no one dials a phone anymore.

royable

(1,264 posts)
3. Simple math processes ("tricks"?) I learned as a kid help me.
Fri Jan 1, 2021, 07:25 PM
Jan 2021

In my head, I think,

8 x 113 =
8 x (100 + 10 + 3) =
800 + 80 + 24 =
880 + 24 =
904

or alternately, handling the 10's place first,

8 x 113 =
8 x (11 * 10) + 8 * 3 =
88 * 10 + 24 =
88 * 10 + 2 * 10 + 4 =
90 * 10 + 4 =
904

Something like 8 * 98 is easy, since it's 8 * (100 - 2) = 800 - 16 = 784.

But then, I think I was born odd.


lillypaddle

(9,580 posts)
4. Must be where I went wrong
Fri Jan 1, 2021, 07:28 PM
Jan 2021

I did the old fashioned/ old school 8x3, carry the 2, etc. Your way is how my 8 yr old granddaughter does it. But that must be why god gave us calculators.

royable

(1,264 posts)
6. Oh, I learned the old school method in ... old school. That's what I'd do with pen and paper
Fri Jan 1, 2021, 08:56 PM
Jan 2021

especially for a more complicated calculation. What I was describing was some mental shortcuts I can take for something that is just difficult enough that I can't do the old school method in my head, but not so difficult that I can't do it in my head at all. I break the problem down into a few chunks that I can keep track of without writing anything down. Now if you'd asked for 438*113, I'd be going for the pen and paper, or a calculator.

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