[InterceptPoint]

My head hurts after that.
+++++++++++
It should. Here is the correct mental calculation for 26 + 17:

7 + 6 = 13
20 + 10 + 13 = 43

[RadiationRomeo]

I use plenty of tricks to add numbers quickly, so I get the logic in the second problem.

BWTH is the first math problem? I don’t understand at all what they are trying to do.

[eclecticEel]

Maybe, but then this is the way my brain works:

20 + 10 + 2*7 -1 = 43.

It’s not really the type of thing to be teaching kids though.

[BradyLS]

My head hurts after that.
+++++++++++
It should. Here is the correct mental calculation for 26 + 17:

7 + 6 = 13
20 + 10 + 13 = 43

Glad you posted that. That's how I do it, too.

[IronJack]

I was thinking 7+6=13, carry 1; 1+2+1=4; 43

Or 26 + 14 = 40, + 3 = 43

Or 26 + 10 = 36, + 7 = 43

I like the first one best.

[logitech]

It should. Here is the correct mental calculation for 26 + 17:

7 + 6 = 13
20 + 10 + 13 = 43

I always liked doing by fives
25+15=40 Then the leftovers 3 40+3=43

Anything but their convoluted way.

[Hoodat]

Here is the correct mental calculation for 26 + 17:

17 --> 1 + 7 = 8
26 - 8 = 18

18 --> 8 - 1 = 7
Take the square of 7:
7 * 7 = 49

Put the two numbers in bold together:
18 & 49 --> 1849

Now take the square root of 1849 and you get 43. Simple.

[wastedyears]

When and where did you learn to do math like that?