## Tuesday, September 23, 2014

### Number Bonds

I mentioned number bonds in a previous post, and now I'd like to give some examples of games you can play at home.

First, though, why are number bonds such a big part of Singapore Math? You may be more familiar with the term "fact family". While similar, there are some important differences. Number bonds really help students see that numbers can be broken into pieces to make computation easier, and they recognize the relationships between numbers using models (first concrete, then written).

This is very important when children get to the stage where most of the students are in my class - being able to work out "hard" addition and subtraction problems (with or without regrouping). They need to be adept with strategies to compose and decompose numbers to make it easier to do the computation, always looking for ways to make ten.

Now, here are some simple and fun ways to practice number bonds at home.

Play Salute! - Three players needed. Player #3 says, "Salute!" and players #1 and #2 each pick up a card, and without looking at it, place it on their foreheads. They can see what each other has, but they do not know which card they are holding. Player #3 (who can see both cards) mentally adds the cards together and says the sum out loud. Once Player #3 has said the sum out loud, Players #1 and #2 each try to figure out what card he is holding. So if the sum is 16, and Player #1 can see that Player #2 is holding a 10, he can perform a mental subtraction equation to figure out what he has (16-10=6).

Throw two dice and tell how many more you would need to make 10. (On the rare throws of 11 or 12, the answer is a negative number.)

Throw three dice and tell how many more it takes to make 20.

Using a deck of cards (ace through 10), turn up one card for tens place and one card for ones place to make a two digit number. How many more to make 100?

Play 10's Concentration (this one is very popular in class) - Place 20 cards face down in a 5 by 4 array. In turns, each player turns up two cards. If they add up to 10 she gets to keep them and try again. Replace holes with two new cards.

Here's a variation on "make 100" above, using a deck of cards. In class today, groups worked together to make 100 using pre-made number cards. There was a lot of great discussion on why the partner for 23 was not 87, (which was what every child thought at first). I love looking for those AH HAH moments, and then having children explain their thinking.