Subtraction is killing us.

[truebluexf]

We used to use RS, and the subtraction bit threw us off. Then we moved, had a tumultuous year, and I'm trying to get back on track. DS is just having so much trouble with it. I've done some MM (which brought tears), we are now doing SM 3a, and I even have SM 2b to help with the patches we missed last year. He just completed the 2B section on subtraction, but it's just not clicking? Subtracting 98, 97, 96, etc should be really easy. He was always a math whiz so I'm stumped. What else can I do? RS games? IP? I want to move on, but we are obviously going to need to remediate subtraction as we go along. We've already spend 6 weeks on this stuff, and DS is getting weary, so I don't want to park on it...I think moving into multiplication will be a good thing. Just not sure what the best course of action is for solidifying subtraction more. Computer games? I should add we are talking mental math type stuff, not multi-digit subtraction with borrowing. Thanks!

 

I just remembered all the drill sheets from RS C...I'm copying them now, maybe he needs more practice with the basic basics? Any other ideas?

Edited October 13, 2010 by truebluexf

[coffeefreak]

Have you tried "Touch Math?" My oldest couldn't add or subtract until we taught her using touch math. I will say though, we do tic marks instead of counting backwards for subtraction.

 

So, let's say you have 10-3=?

 

You would touch the 3 and say "3" and then make a tic mark while counting up, "4 (tic), 5(tic), 6(tic), 7(tic), 8(tic), 9(tic) 10 (tic). You would have 7 tic marks, showing him that 10-3=7. Either way would work.

 

Sometimes, we have to give them a way to get the answer until they mature a little more, just so they can move on and not be frustrated.

 

HTH!

Dorinda

[wy_kid_wrangler04]

Try this for a fun way to subtract

 

and try this for extra lessons

 

These are free :001_smile:

[sagira]

Remember that Math Mammoth has practice sheets as well you can print out depending on what your dc need. Good luck!

[SnowWhite]

Have any of your curriculum programs taught *strategies* for subtraction? BJU Math, which is my favorite BY FAR is very strong in that regard.

 

For example, when you are subtracting just a few, count backwards. Check to see if the problem is near a double (like 13-7... if it were 14-7 it would be a double). See whether you are subtracting a number near the original... for example 8-7 is subtracting the "next door neighbor", so the answer is one. If you are subtracting 9, the answer will be one more than if you're subtracting 10... so 35-9 is one more than 35-10.

 

I know Math U See is fabulous about teaching strategies as well.

[truebluexf]

Thanks....yes we did strategies, but perhaps we need to go back to the beginning with that. That could be the hole I'm looking for, now that you mention it. We did it so long ago, and took too long of a break, I think.

[swainsonshawk]

Another thing my son learned from Singapore math that I don't even remember teaching him is this:

 

15-8=

10-8=2

2+5-7

so, 15-8=7

 

These are easy and fun for him to figure out because he knows his tens facts down cold. He does almost every larger subtraction problem in his head this way and is really fast.

 

I would also say don't get too hung up on the mental math of Singapore. It's a great skill to have, but it's early (in my opinion) for some of those "tricks" to stick. My oldest I had just write the math subtraction out on a piece of paper and figure it out, even if I thought it should be obvious (like 200-98). When your child is more familiar with money it will be easier for him to figure out quickly.

 

I say file it in the back of your head for future study and move on to the next topic.

[truebluexf]

Thanks...you're right. :) I think I'm just stressed because I know we never really completed last year, and I don't want him to have any big holes from that and switching curricula. I think we'll just move on, and have him do one of RS C's drill sheets each day. They take about 2 minutes (if that) to complete, but will help drive home the facts for the time being (and he loves being timed, so if I do them as "time trials" he'll love racing against the clock!). I just love that he has mostly learned so much mental math, more than I was ever good at even grades ahead of him!

[5LittleMonkeys]

15-8=

10-8=2

2+5=7

so, 15-8=7

 

These are easy and fun for him to figure out because he knows his tens facts down cold. He does almost every larger subtraction problem in his head this way and is really fast.

 

 

 

MUS teaches this way also. I don't think there is one right way to have your son do subtraction. I actually have my dd7 do her subtraction with many different methods. I will have her use the MUS method to do about 5 of them, have her turn the problem into an addition to answer 5 of them and then have her use count up or down with some of them. We also usually do a few with some type of counters. I wouldn't park on this any longer. You can always do subtraction work for a few minutes every day while moving on with something else. It may just be a matter of letting it stew in his head for a while before it finally clicks.

[Spy Car]

I would have him walk back though a number of subtraction problems using both the mental strategies and the standard algorithm (subtracting in columns) with him explaining what he was doing in terms of strategy and procedure. Having him describe the number in terms of the number of Hundreds, Tens, and Ones (we say Units) rather calling 3 in the Tens column "3" or even thirty (which is acceptable) but better 3-Tens.

 

If he is narrating what he is doing you can see where he is going wrong, and can ask leading questions to get him back on track.

 

Bill

[siloam]

Amy,

 

If I were in your shoes I would go back to whole parts circles, and some sort of manipulative. If you still have an Abacus that would be great, but popcicle sticks, M&M's (if they stay around long enough) ;) or anything tangible to get it back in his head.

 

I would also do drills of "8 + what =10, and 10-8 = what" after showing him whole to parts circles and how subtraction and addition are opposites of the same function.

 

Heather

[truebluexf]

Thanks. :) I'm doing RS B with DD1 so we have it all. :) I think I'm going to move on to multiplication while spending a few minutes each day on the subtraction stuff, kind of like RS warm-ups. ;) I don't want to hang back and get behind, but I don't want to just let this go, either. I think it's a fluency thing. I hate that the last 3 months or so of school for us last year were practically nil because of our situation. It was just too much of a break, bc we made it all the way through subtracting in columns in RS C, so I know we covered all this mental subtraction stuff!! We should probably play some subtraction corners, too! He loves that game, duh!

[Sara in WA]

Is this your 8yo? I had a similar issue with my dd, now 8yo. Until very recently, she had a difficult time calculating math facts. I saw a big change after about 4 weeks of school work this fall. I attribute this change to three things. One is that she has matured over the last year. The second is that she is now attending a PT classical school that uses Abeka, which is awesome in it's drill. Lastly, she is required to do math flash cards at least 4 days a week. I think this combination has been key for this child. Drill, drill, drill.

 

We used Singapore for homeschooling, which I just love. Are you new to Singapore? If so, you may want to try and peek at the earlier books to get some tips on subtraction. My youngest dd is in 1A, and even in there you'll find some great lessons on subtraction.