Stuck with Singapore Essential Math B.

[LadyBelle]

So we got to the subtraction part. and we've hit a road block. I am confused on how to teach this. They have jumped to subtracting numbers bigger than 10. How am i supposed to do this. My daughter just got te hang of crossing out and counting backwards to get to answer. Did I miss a very important step here. How is she supposed to get to the answer using double digits. using the number line at the top of the page when they first introduced subtraction. She uses a lot of finger counting as well with adding. for ex, 5+2, she'll put 5 in her head, and then count each finger until she gets to two fingers up. so 5... 6, 7.

 

Any help on teaching these to her. I wish there was some kind of help on this.

She's 6 btw.

[chicagoshannon]

If I understand the question correctly, I think you're supposed to have her separate the number to make a 10.

 

For example: 20 - 12 would be 20-10-2. So 20-10=10 then 10-2=8. Or you could break it down to 10-10 and 10-2.

 

Or 20=10 and 10. And 12= 10 and 2 then subtract.

[poiema]

What chicagoshannon is talking about doesn't come up until later, I think in 1b. In Essentials, we just used the number line at the top. Counting back. I have also taught my kids to start with the lower number and count up. Subtraction is very brief in Essentials, so counting on or backwards is fine.

[LadyBelle]

I see.... they kind of just threw the double digit subtraction in there and didn't want to confuse her.

Is there anything I can do to prepare her for when it comes back in 1a/1b

[Five More Minutes]

I see.... they kind of just threw the double digit subtraction in there and didn't want to confuse her.

Is there anything I can do to prepare her for when it comes back in 1a/1b

 

To prepare for 1A (on top of using Essential Math), I recommend using c-rods and doing some of the activities that Rosie shares at Education Unboxed. I often expanded the lessons at the bottom of the pages of the Essential workbook to include some of these activities, making the concrete part of the lesson last longer.

 

When they hit subtraction in 1A and 1B, they need to understand in a very concrete way what it means to break apart and regroup 10s. Counting on / back (using a number line) is always a strategy taught for adding / subtracting 1, 2, or 3, but the powerful methods introduced later on require students to be able to take from the 10 or make a 10. Playing with c-rods is an easy, effective way to build this understanding.

 

ETA: Singapore 1A will build up to this type of subtraction, but I just found it so much easier when my dd already was familiar with how numbers are composed.

[myfatherslily]

Cuisenaire rods or just something to count with. I often just grab a pile of whatever's handy, like pencils. You have 11 Legos. Now take away 5. Just play with different ways and see if she gets it. My kids did better when I said "6 take away 3" rather than "6 minus 3". If it's too confusing, take a break and go back to it after a little while.