We looked at how to add or subtract a multiple of 10 from a 2 digit number. You can use a 100 square to help you count on or back in jumps of 10.
We looked at adding and taking away to/from a 2 digit number by partitioning and counting up/down on a number line.
We tried to use these methods in our problem solving.
Some of us are getting very good at using these informal methods, recording and explaining our ideas.