Decomposing and composing to the hundreds place
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Students learn to decompose and compose numbers to the next hundred from random numbers.
Students will be able to decompose and compose hundreds (100, 200, 300, ...) from round and random numbers.
Complete the number lines with the students. They count in jumps of 1.
Explain how to use the MAB blocks to help represent tens and hundreds. When you compose to the next hundred you look to see how many more hundreds you need. Show an example that you can easily compose to a hundred if you know how to compose to a ten. Students complete a number bond chart of 100 with the number bond chart of 10 next to it as support. Explain that when you compose hundreds and tens you need to look to see how many tens you need. When you compose from a tens number to a hundreds number you skip count in tens or hundreds. If you start from a random number you count on to the next ten and then use skip counting. Students practice composing numbers in different ways dragging both money and MAB blocks. Also show how you can show composing by jumps on the number line. Ask them to fill in the missing numbers from a decomposition and then complete the number bond chart. Students need to decompose the numbers in their heads.
To check that students understand decomposing and composing numbers to the nearest 100 you can ask the following questions:
- What can you use as a good example of composing? (money)
- How can you easily compose 200 from 146? (first count on from the ones, then move to tens)
Students practice composing by dragging money to compose the desired amount. Then they practice decomposing hundreds numbers in a number bond chart without visual support.
Ask students to fill in the decompositions of 200 and discuss that it is useful to be able to compose to hundreds. Can the students come up with other situations in which this would be useful?
Students who have difficulty composing to hundreds can use money or MAB blocks as visual support. They can compose with bills and count on to the desired number. They can do the same with hundreds, tens and ones of MAB blocks.
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