Was this how you learned to add multiple-digit number together?

[Hoosier8]

Even though my major was pure math, I still have trouble ciphering. I ended up learning how to add and subtract left to right instead of right to left. It is much easier, much quicker to factor large lists of numbers for addition. No carrying ones.

 

[eldirector]

They taught me "brute force" addition in grade school. I later taught myself both the method in the OP and Cathy's. I use whatever works.

I honestly don't see the issue. The more methods you are familiar with, the more problems you can solve.

It's like how I calculate tips:
1) move the decimal to get 10%
2) if I want to tip 15%, take about half of step 1, then add them together
3) if I want to tip 20%, simply double the value in step 1
4) round to the nearest half-dollar, so I can calculate the total bill without doing much more math

I could do long-hand multiplication, but why?

 

[Mr Evilwrench]

At my son's elementary, they use a program called "Everyday Mathematics" which assaults the young skulls full of mush with a few different additions and subtractions, and three or four different multiplications and divisions. They spend very little time on any given one, and for practical purposes approach the curriculum sideways, trying to do the whole thing all at once for the whole year. This confused my son terribly. He's just not very good at maths to start, and there was no way to latch onto something that suited him when it was presented as a firehose to the face. I finally printed out worksheets and taught him the right way to do them all (and don't do it any of those retarded ways!) which allowed him to calm down and feel some sense of mastery.

This program was, for some reason, bought by the PTO above and beyond the normal curriculum, but I suspect it was brought to them by some snake oil salesman that gets kickbacks from these recovery centers that purport to help. The tell was when we were discussing the problem with the guy that ran the place and I said we wanted to get around the "Everyday Mathematics" stupidity, and he told me that was what they use there, they just do it harder. We didn't need that. I think the PTO were scammed.

 

[churchmouse]

They taught me "brute force" addition in grade school. I later taught myself both the method in the OP and Cathy's. I use whatever works.

I honestly don't see the issue. The more methods you are familiar with, the more problems you can solve.

It's like how I calculate tips:
1) move the decimal to get 10%
2) if I want to tip 15%, take about half of step 1, then add them together
3) if I want to tip 20%, simply double the value in step 1
4) round to the nearest half-dollar, so I can calculate the total bill without doing much more math

I could do long-hand multiplication, but why?

Do you balance your check book that way???

No knock as I use near the same mental method myself. Break it in half (half dollar) and round to the nearest 10's. Works for me but not in the totals column in the check book.

Kids need to know straight up math.

 

[eldirector]

Do you balance your check book that way???

No knock as I use near the same mental method myself. Break it in half (half dollar) and round to the nearest 10's. Works for me but not in the totals column in the check book.

Kids need to know straight up math.

I use whichever methods solves the problem. My checkbook requires a bit more accuracy and does NOT require speed. I'll do that long-hand.

Sticking with the "money" theme: If I only have a little cash on me, and want to see if I can buy a couple of little things, I need to get a rough idea of the total with tax a bit quicker, but I do NOT need any real accuracy. The nearest dollar or so works fine. So, break it into close representations that are easy to add, and then use 10% for tax (round the 7% up), and viola! What's really funny, is that dropping the "cents" and then using a larger value for tax tends to total within a few cents of the actual total if you do it long-hand.

I often see folks struggling to add $3.99 and $2.89 together. Lots of carrying of 1's and such. It is $4 plus $3 minus 12 cents!

What's the old adage? If you only have a hammer, every problem is a nail?

 

[Lucas156]

It seems we are tailoring the learning methods to the slowest learners in the class. I can personally tell you that if my college algebra professor saw you doing that they would tell you it's the wrong way and not the way it is done in college for obvious reasons(takes too long, tedious). I can see doing it that way in my head but try to use that method to add ten digit numbers and it will take you ten times as long as writing it out the "regular way". We are setting our kids up to fail in college.

 

[Goodcat]

I like it. This is how I do it in my head.

 

[Double T]

I got docked in school for not showing the work the way the teacher did it. If you give me two numbers I have crazy ways of deducing the answer that are correct. Multiplication is the most difficult to explain though for me on paper, division as well.

Of course, I got into trouble in physics for using calculus to give a more exact answer than was needed as well. Darn AP chem and calc will make you be more precise than needed. LOL

 

[gstanley102]

I don't see a problem with it if the teacher understands the method, and can teach it
as well as the standard method.

 

[churchmouse]

I use whichever methods solves the problem. My checkbook requires a bit more accuracy and does NOT require speed. I'll do that long-hand.

Sticking with the "money" theme: If I only have a little cash on me, and want to see if I can buy a couple of little things, I need to get a rough idea of the total with tax a bit quicker, but I do NOT need any real accuracy. The nearest dollar or so works fine. So, break it into close representations that are easy to add, and then use 10% for tax (round the 7% up), and viola! What's really funny, is that dropping the "cents" and then using a larger value for tax tends to total within a few cents of the actual total if you do it long-hand.

I often see folks struggling to add $3.99 and $2.89 together. Lots of carrying of 1's and such. It is $4 plus $3 minus 12 cents!

What's the old adage? If you only have a hammer, every problem is a nail?

Bingo.

 

[88GT]

There are several problems with it. First, it's a poor methodology. The concept is sound but there are better ways of showing kids how to break apart multi-digit numbers than that. Like I said, I did this everyday for two weeks with my kid when we got to multi-digit numbers addition/substraction. We still have to go back to it sometimes to "remind" him. Second, this is not an alternative method of addition. It is a supplement. It's use is limited as a way to help those struggling with the abstract see it in concrete terms. For that I applaud the effort to help children see it that way. Third, it is not a sound method for addition of more than two or three numbers. It becomes far to cumbersome and inefficient for accuracy. It may still be a great means of estimating, but this is not an exercise for estimation, something some of you fellas can't seem to grasp.

There's also the high likelihood that the teacher is not connecting the dots for the students. If the students simply think this is another method of addition, they will necessarily miss out on the benefit of using it because it isn't being put into context. WHY are they breaking the numbers down into their place value components?

Then there's the issue with the higher level math that employs addition. Take multiplication. Multiplication of multi-digit numbers requires addition. Just imagine what what the process would be to multiply 536 x 42 if the student did the addition part of the process using the decomposition method.

 

[JAH]

I ran into a similar situation when I went back to college for my degree. The way math was being taught was lost on me. However I did remember how I learned it originally. Now my son brings home algebra and gets his elder brother to tutor him.

 

[eldirector]

There are several problems with it. First, it's a poor methodology. The concept is sound but there are better ways of showing kids how to break apart multi-digit numbers than that. Like I said, I did this everyday for two weeks with my kid when we got to multi-digit numbers addition/substraction. We still have to go back to it sometimes to "remind" him. Second, this is not an alternative method of addition. It is a supplement. It's use is limited as a way to help those struggling with the abstract see it in concrete terms. For that I applaud the effort to help children see it that way. Third, it is not a sound method for addition of more than two or three numbers. It becomes far to cumbersome and inefficient for accuracy. It may still be a great means of estimating, but this is not an exercise for estimation, something some of you fellas can't seem to grasp.

There's also the high likelihood that the teacher is not connecting the dots for the students. If the students simply think this is another method of addition, they will necessarily miss out on the benefit of using it because it isn't being put into context. WHY are they breaking the numbers down into their place value components?

Then there's the issue with the higher level math that employs addition. Take multiplication. Multiplication of multi-digit numbers requires addition. Just imagine what what the process would be to multiply 536 x 42 if the student did the addition part of the process using the decomposition method.

You got all of that from that linked page in the OP? I just saw a single example of a single method, a "funny" answer to a question, and a comment attributed to the "teacher".

 

[AnnieO]

My son (third grade) insists it is easier to add
374+271

than
374
+271
-----------


He has trouble carrying the one to the hundreds column. However, I make him do it that way sometimes because I fear he will have problems down the road with more advanced math. And he says he likes addition.

 

[CathyInBlue]

That's the way I'd normally do it.

For mental math, I'll often round up, add up the round-offs, then subtract them from rounded estimate.

For example, rather than column-add 99+99+99, I'd just round each up to 100, total 300 and subtract 3-- way easier to get 297 THIS way.


I'm always amazing how so many folks were never taught tricks like this that are so functional in every day life. Math is everywhere, and while you may not being crunching partial derivatives and Riemann sums on a daily basis, learning practical math WELL is of great value.

I tried to make tips, tricks, and techniques inherent to my math lessons when I was trying to do the teaching thang, and that's just the kind of thing I taught.

I maintain that there's virtually never a reason to do math with digits larger than 5. 99 + 99? So many big digits! Screw that. 100 - 1 + 100 - 1. Now all of the digits are ones and zeroes.

 

[CathyInBlue]

My son (third grade) insists it is easier to add
374+271

than
374
+271
-----------


He has trouble carrying the one to the hundreds column. However, I make him do it that way sometimes because I fear he will have problems down the road with more advanced math. And he says he likes addition.

Try making him do his sums on graph paper, one column per decimal place.

 

[Hohn]

They taught me "brute force" addition in grade school. I later taught myself both the method in the OP and Cathy's. I use whatever works.

I honestly don't see the issue. The more methods you are familiar with, the more problems you can solve.

It's like how I calculate tips:
1) move the decimal to get 10%
2) if I want to tip 15%, take about half of step 1, then add them together
3) if I want to tip 20%, simply double the value in step 1
4) round to the nearest half-dollar, so I can calculate the total bill without doing much more math

I could do long-hand multiplication, but why?

This is the method I use, too-- exactly.

 

[HeadlessRoland]

[video=youtube;Vetg7vWitTU]http://www.youtube.com/watch?v=Vetg7vWitTU[/video]

 

[Hoosier8]

[video=youtube;Vetg7vWitTU]http://www.youtube.com/watch?v=Vetg7vWitTU[/video]

342
173

Left to right.

3 minus 1 is 2, since the next column since 7 is larger than 4 subtract 1 from 2 to get 1, if the lower number was smaller than the upper number it would not change.

Since the next column 7 is larger than 4, subtract 7 from 10 which is 3 and add to 4 which equals 7, since the next column the 3 is larger than the 2, you subtract one from 7 to get 6.

The last column, subtract 3 from 10 to get 7 and add to 2 to get 9.

No carrying ones. Quick and easy.

 

[hopper68]

What difference does it make?? Is this not what calculators are for? And would it not be easier for kids to tell time if all clocks were digital?