Learning To Add

Part of the Grade 2 number sense and numeration expectations are around being able to add and subtract numbers using a variety of strategies.  Steve's class has been working on using mental math as a strategy and he wanted to see what other strategies the students were using to help them add numbers together.

His lesson started off with a minds-on activity where the students had to talk about how they would go about adding three numbers together.  He did a think-pair-share activity where the students had to tell their partner how they would add the numbers together.  To help tie in a little more accountable talk, the students were then asked to share what their partners' strategy for solving the equation was.  "John" was asked why it was okay for his partner to move the 3 around in the addition sentence.  He told the class that because it is addition, it doesn't matter what order you add them in.  This thinking was recorded on the board to help with the upcoming problem.  Here are some of their strategies:

The students were given the following problem for their action part of the lesson: 

I went to the store and bought some stickers.  One pack had 14 stickers, one had 7 stickers and the last pack had 16 stickers.  Did I buy enough to give everyone in the class a sticker?

Working in pairs, the students quickly went to work adding the number together using different strategies.  What was interesting is that most of the students were successful in solving the problem, but didn't actually answer the question with a final sentence.  For some students they realized that the number they got was different than the number of students in the class, (the number of stickers purchased was higher than the number in the class) and they said that he didn't buy enough.  This was talked about with the whole class during the consolidation of the lesson.

For consolidation, the student's work was grouped together in a bansho to highlight the strategies that they used.  In total, the class showed 5 different ways of adding.

Pictures, Tally Marks and Tally Marks in groups of 10 (this was highlighted to get the students to think about groups of rather than just making groups of 5)

Adding by 1s and 10s is the "traditional" was of adding, and the final way was Using friendly numbers

For the group that used friendly numbers, they were prompted by the teacher in helping to explain their thinking.  Orally they were able to communicate what they had done, but were not quite able to record it on paper.  So when they became "stuck" the teacher recorded their thinking in pen for them and then they carried on from there.

As an "exit ticket" out of the lesson, the students were asked what strategy they would try next time they did addition.  What was great was that the students were keen to say "I used strategy x, and next time I want to try strategy y because..."  This shows that they are reflecting on their learning, and hoping to expand their addition tool kit.

Everybody Add and Subtract Now!

The afternoon Grade 2 PLC asked to look at different strategies they could use to teach addition and subtraction to their class.  The group had some great discussions about the pros and cons for teaching the different strategies and also for ways to try the strategies out in the classroom.  One discussion was about how great it would be to divide up some of the strategies to make them be "must covers" for different grades.  This way, as the students progress through the grades and into higher numbers in addition and subtraction they would already have some strategies in place, and be able to add strategies to their tool kit.  See which of the strategies you are familiar with, and see which ones will be added to your tool kit.  If you want to learn more about addition and subtraction strategies I highly recommend reading "Young Mathematicians at Work:  Constructing Number Sense, Addition, and Subtraction" by Cathy Fosnot.  You can get the book from Pearson.  The ISBN is: 0-325-00353-X