"New" Method of Addition - Could Someone Please Explain it to Me in Step By Step Detail?

There was some really stupid and misleading video that used this example. But it's a really bad example.

It's a way to subtract by adding. People do this all the time. I bet you do it too. Here's an example:

Say your father was born in 1965. How old will he be on his birthday this year? Will you take 2014 - 1965, write that down, and do it the old fashioned way? Probably not. Most people will think, well, it's 35 years from 1965 to 2000, and 14 years from 2000 to 2014, and 35+14 = 49. So the answer is 49.

The example you show has too many steps. What's with going to 15? That's just stupid. The video is trying to discredit a method everyone uses naturally, probably without ever being taught it. I think it's another right wing piece of propaganda to discredit the "core curriculum," but let's not get into that.

First of all, 32-12 is pretty obviously 20. Most people would do that in their heads, not even the old fashioned way. If you want to use the "new" way, you'd go to multiples of 10, as you noted.

12 to 20 is 8

20 to 32 is 12

8+12=20 is the answer.

Going 12 to 15 is 3, etc., just introduces an extra, unnecessary step. The only reason to do that is to complicate it so you can make fun of it.

Here's a better example:

67 - 39

39 to 40 is 1

40 to 67 is 27

1 + 27 = 28.

Quick and easy, and it avoids having to borrow 1 from 6 leaving 5, subtracting 9 from 17 to get 8. Then subtracting 3 from 6, umm, I mean 5, to get 2 and getting 2+8, umm no, 20 + 8 = 28.

You tell me which way is easier.

People do something similar when making change. You pay for something that costs $3.83 with a $5 bill, and they do:

say the total, 3.83

give you 2 cents and say 84, 85

give you a nickel and say 90

give you a dime and say 4 dollars

dive you a dollar and say, And 1 is 5.

Change was 1.00 + .10 +.05 + .02 = $1.17 without even calculating the number.

Subtracting is the same as adding negative numbers.

The new way is something handy to know if you plan on doing mental math, but looks ridiculous on paper.

The "new" way has you crawling your way from 12 to 30 to see what's in the midd.e

It starts adding 3 to go from 12 to 15.

Then adds 5 to get to 20

Then adds 10 to get to 30

then adds 2 more to get to 32.

Then you add up the steps you did along the way, 3 + 5 + 10 + 2 = 20

I agree this is completely silly. They are forcing this new way on all kids, even if they have a full understanding of the old way, just because some kids may have a better grasp at the new way vs. the old way. Instead, learning should be customized for each kid. Find out what works for them and let them go.

This is kind of like the way I was taught to make change. Suppose you are a clerk in a store and someone buys something worth $3.95 and hands you a 5 dollar bill. You could try to work out the subtraction problem

5.00 - 3.95

but it's easier to just start handing the person change.

You:

OK, that's 3.95

and a nickel (5 cents) is 4.00

and a dollar is 5.

What did you do here? you counted up from 3.95 to 5.00 to work out the amount of change.

In your example:

That's 12

plus 3 is 15

plus 5 is 20

plus 10 is 30

and 2 is 32.

You added, 3+5+10+2 = 8 + 10 + 2 = 18 + 2 = 20

So 32 -12 = 20.