frustrated, stuck with multi-digit multiplication - suggestions?

[AJP]

My son is 10, and has been using Math U See for the past couple of years with great success. Right now he's near the end of the Gamma book, and keeps having the same problem over and over with multiple digit multiplication. He isn't keeping it straight where each digit goes when writing out the problem, keeps mixing them up, not regrouping properly, etc., and of course ends up with incorrect answers. This is causing him anguish. Math has been easy and fun for him until now. I don't want to cause him to hate it permanently, but I'm at a loss as to how to help him get this concept nailed down and progress. He wants to progress. He understands place value to a certain extent, he can write out large numbers using place value notation (i.e. 1,020,713 = 1,000,000 + 20,000 + 700 + 10 + 3), he knows the multiplication tables through the 10s by heart. When he goes to write out a multiplication problem that's more than 2 digits x 1 digit, he gets all mixed up about where all the numbers go. The Math U See lesson DVD is no help, we've watched the relevant lessons together a number of times. I keep showing him how to do it, trying to explain it in different ways, using lined paper turned sideways or graph paper as an aid to keeping columns and rows straight, but it doesn't seem to help. I tried to check the Math U See forum on their website for tips, but it says it's closed for maintenance.

I tried backing off entirely for a while, he did no multiplication at all for several months. I'm not sure if he's just not developmentally ready for this yet or what. I remember myself at his age not doing quite this level of math, at age 10 we were still on single digit multiplication and memorizing times tables (I don't know how that compares to today's school standards, we're independent and I try not to gauge his progress by public school standards, but it's hard not to compare to where I was at the same age). However, he wants to move on to more advanced stuff, including division (Math U See doesn't introduce division until the next level after this one), and I think he needs to get this nailed first. There were some times during my school years when some crucial aspect of a math concept wasn't fully understood before moving on and it caused problems later that had to be remedied in order to progress. I'd rather avoid that with him.

I'd love any suggestions for helping him with this - links, tricks, etc., or just a different perspective. His personality tends towards perfectionism, and often he decides he'd rather not do a thing at all rather than do it "wrong" or not get the results he was hoping for, I have to tread carefully with him in that respect. Help?

[morgainesmama]

There are LOTS of ways to teach multidigit multiplication.

The easiest way is to break it down and add -- and it's really visually understandable for many kids who don't get the abstraction of where to put the numbers.

That is -- 27x9 = 20x9 + 7x9.

32-95 = 30x95 + 2x95 OR (30x90 + 30x5) + (90x2 + 5x2).

My daughter does a thing in everyday math where they multiply in grids diagonally -- I haven't explored it very carefully since my days in "Teaching Arithmetic" as a college freshman.

My son doesn't quite get *where* the carried numbers, etc. go when multiplying (and we're only on 2 digit x 1 digit numbers; he's also only 7) but when I lay it out, then show him the alternative of how to arrange the problem visually, he grasps it 85% - 90% of the time.

[Altair]

Everyday Math teaches the Lattice/Matrix, which is the diagonal one you're referring to-- it is an easier algorithm than the traditional one, but it has the same problem of not using any number sense to get the answer so it's just rote memorizing a method.

I like the partial products one better (also everyday math).

24
x35
____
20x30= 600
20x5= 100
30x4= 120
5x5= 20
+_____
840

The cool thing with this one is once you get quick at it you can do it in your head. And the 4 part addition at the end is so easy you can do it mentally. I see a lot of kids who don't write out the steps, it just looks like this:
24x35= 600+100+120+20=840

[kathymuggle]

24
x35
____
break it down: 24 x 30, plus 24 x5

24 x 3= 72. Therefore 24 x30 = 720
If you cannot do this in your head, break it down: 24 x2, plus 24.



24 x 5=?

I know 24 x 10 = 240, so 24 x5 is 1/2 that....120.

720 + 120= 840

Both of my older children use a variation of the above to come to lutiplcation answers. The whole carrying, lining up ones and tens columns, and adding zeros to second and third lines is not clean enough for them.

They are both fairly strong in math, and very good at mental math.

They do something similar for division and it works great!

I think it builds number sense better than the formulaic way most of us were taught.

[ikesmom]

My ds has a hard time keeping things straight most of the time too..you can use graph paper. You can use it for writing or spelling too.

I saw this link when looking for an easy way to explain estimation and although it is for 8th gr. I was able to explain to ds easily. http://arb.nzcer.org.nz/supportmater...n.php#rounding

[kewb]

My son prefers the lattice method when dealing with large multi-digit numbers. It ended major headaches when we discovered this.

[moominmamma]

If he's pretty much got the algorithm but is just having trouble remembering which place value he's multiplyiing through, you could try using colour:


5321
x346
_________
31326
212840
1596300
_________
2840466


You can use graph paper and shade the boxes the appropriate colour with pencil crayons, or else give him pens of different colours to work with.

Miranda

[AJP]

Thanks for the great ideas! He prefers to figure it out in his head, and I think some of these tricks might make it click for him a little better. He and I seem to process numbers differently, so it's been a bit of a challenge for me to explain concepts to him. I need to not get caught up in making him 'show his work' as long as he gets the right answer.