Reflection: Intrinsic Motivation Extending Partners of 10 and 100 - Section 4: 100th Day Activities

Watching students grapple with mathematical reasoning is one of the most exciting things to do as a teacher of mathematics. Today students were faced with the task of counting out and measuring 100 pennies and 100 snap blocks as two of the tasks. They also had to take a 2-digit number and then count base 10 blocks to reach 100.

I watched the different strategies that the children employed. One group decided to make the 100 snap blocks in a long line, but they put a purple block at every ten so they could easily count 10, 20, 30, 40...   Another group decided that they could make towers of 10 to keep track of how many they had and then they could put the towers together and measure it.

One group was measuring with a tape measure but the tower of 100 was longer than 60 inches. They came and asked me what to do to which I replied, what can you do? Suddenly one of the boys said, I can just move the tape measure every inch. He moved the tape measure and measured each inch using the 59 to 60 portion of the tape measure. I might have told him to mark and move the whole tape measure, but his strategy worked and they were able to find the total in an adequate way.

With the 2-digit number and the base 10 blocks, one group had the number 22. They picked up 88 blocks but when they counted it was too high. They knew to take away 10 of the blocks to get 72. They did the same thing with 65 and 45 blocks. Suddenly one of the children said, wait, if I want to get to 100 and I just have to go down one 10 because of the extra ones!  YES!! Her partner quickly said well then if I have 79, I don't need 31, I would need 21.

As teachers we often jump up and try to tell kids what to do, but what we need to do more of is step back and watch. Let them figure it out. They will then be building a more lasting understanding of numbers.

Mathematical Reasoning
Intrinsic Motivation: Mathematical Reasoning

Extending Partners of 10 and 100

Unit 8: Numbers Have Patterns
Lesson 3 of 14

Big Idea: Students know partners of 10. Can you believe that there are partners of 100 and 1,000 too?

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Standards:
Subject(s):
Math, Number Sense and Operations, Algebra, Patterns (Algebra), Place Value, estimate, problem solving, counting
75 minutes

Beth McKenna

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