Number Talks: Friendly Numbers


Number Talks October 27, 2019
Friendly Numbers


This Number Talks involved expressions with friendly numbers. Friendly numbers are single number used to make a friendly pair. These are numbers that make performing operations easy and flexible. Friendly numbers include multiples of 10's and 100's. 
The goal of any NT with preservice teacher to expose them to math strategies that will enhance their teaching and equip them with Mathematics Pedagogical Knowledge. Many school districts in north and central Alabama use NT. Therefore, I want my preservice teachers exposed to various way to solve problems and the ritual of NT. 
 The following is a cluster of problems:
99 +5
99 + 15
99 + 26
99 + 51

99 + 5 is 104
Me: How did you get 104?
Chase: I stack them up 99 on top and 5 on the bottom. Then I just added.
Katherine: I added 1 to 99 to make 100 and then I added 4.
Me: Where did you get the 1 when you added it to 99?
Katherine: I took it from the 5. That is why I added 100 +4.

99 + 15 is 114
Me: How did you get 114?
Chase: I added 100 to 15 then I subtracted 1 to get 114.
Katherine: I used the above problem 99 +5 to get 104 and then added 10.

99 + 26 is 125
Me: How did you get 125?
Katherine: I added 99 +1 and subtracted 26 -1. 99 +1 is 100 and 26-1 is 25. Then I added them together 100+25 is 125.
Erika: I add 100 + 20 + 6. 100+20 equals 120. Then 120+6 is 126. But I subtracted 1 from 126 because the problems was 99 + 26 and not 100 + 26.

99 + 51 is 150
Me: How did you get?
Katherine I took 1 from 51 and added it to 99. 99 +1 makes 100 and added 50
100 +50=150
Chase: I added 99 +50 +1. I took the 1 from the 51. 99 + 50 is 149 +1= 150.

I know these number seem basic. However, I wanted PT to be able to make friendly numbers without using the traditional algorithm as stated in Chase's first response. I want them to use decomposing and compensation strategies in order to flexibly and fluently add problems to make friendly numbers.










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