69) Near Ten
Ten Plus Bonds: Strategy 9+
To develop the strategy of adding 9, by adding 10, then subtracting one, for wholes less than 20.
For example, to solve 4 + 9
Prior knowledge of ten plus bonds, the commutative property of addition and adding and subtracting ten and one is needed.
A little easier
Represent the subtract one
Make the subtracting one explicit by:
- representing the one with a 1 block and
- change the empty frames into an empty number line.
For example, 4 + 9
A little harder
Near ten strategy +9
Play Bonds of 11 to 20: Near Ten Strategy +9 a little harder. In the game students have to add nine to parts that are teen numbers using the same strategy.
The blocks are a scaffold to support calculation. If students can calculate without some or all of the blocks encourage this. Below is a progression of reducing scaffolding, from most to least support, using near ten for 14 + 9.
In the next activity students extend the near 10 strategy to subtracting a part of 11. Go to
Ten Plus Bonds: Bridging Ten Addition, Strategy 8+