Lucky 8 and Lucky 9: Teaching Compensation for Addition Problems in Small Guided Math Groups
Lucky 8 and Lucky 9 refer to the math strategy of compensation – a strategy that fiddles with the numbers in order to make the problem easier to solve. Both the Common Core first grade and second grade Operations and Algebraic Domain, specifically refer to teaching a variety of mental math strategies.
When practicing Lucky 8 and Lucky 9 students are adjusting these numbers to become 10 so that they can work with them more efficiently. Remember that when we are teaching math we always want to think in the frame of concrete, pictorial and abstract.
I use the double ten frame to teach this so students can see what is happening. Look at an example of that here http://www.teachervision.fen.com/addition/graphic-organizers/44540.html I do this in small groups and give each child a double ten frame and counters. They get to manipulate the numbers. So take the problem, 8 + 7. Students see if we have “lucky 8” that there are two empty squares in the first frame where we built 8. So they take two from the second frame and move them into the first frame to make a ten and then we add 10 + 5. We practice this many times so that students get a conceptual understanding of the model. Then we do the same thing with “lucky 9”.
At this site they can practice compensation on the Illuminations site under the Add game http://illuminations.nctm.org/activitydetail.aspx?id=75 On this great site that talks about fact families, you can see a visual of how this works at http://www.montgomeryschoolsmd.org/schools/oaklandes/mathstudentworkpages/gr1un2page6.html
I also do number grid activities to teach this. See post on number grid
Here are two poems that I made up that I use with the students when teaching this strategy.
You’re So Great!
When I see you
I know what to do
Go to the other number
And take two!
You’re So Fine!
Glad to see you everytime
It’s just too much fun
To go to the other number
And take one!
Songsforteaching.com has some great poems as well. They have one called 9 Be My Friend http://www.songsforteaching.com/carlsherrill/9bemyfriend.htm …the first line goes “9 be my friend, let me turn you into a ten…” These are great for talking about the problem and having an abstract mnemonic to remember the strategy. They have another poem called the 9 Rule http://www.songsforteaching.com/jeffschroeder/9rule.htm which also talks about compensation.
Google this “Math 4 – Act. 01: Mental Math: Addition and Subtraction.” It is a UEN lesson plan with a great graphic organizer.
Happy Mathing and Happy Holidays!