Addition to 1,000 by splitting the second addend into hundreds, tens, and ones

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Students learn to add to 1,000 by splitting the second addend into hundreds, tens and ones to add them to the first addend. In this lesson, addition is simplified into addition problems like 620 + 135 (+100 +30 + 5) = 755.

2.NBT.B.7

Discuss with students that it is useful to learn how to add by splitting the second addend. By doing so you make adding larger numbers easier.

Show students an introduction with MAB blocks on the board showing an addition problem. Ask students to solve the addition problem. Then give them a few abstract addition problems to solve. Ask students how they solved for their totals. Give students a story problem and ask them to give the answer. Erase the grey blocks to show the answer.

Explain to students that they can add by splitting the second addend into hundreds, tens and ones, and add those separately to the first addend. Discuss that a hundred is a group of 100, the tens is a group of ten, and that ones are the numbers 1-9. Next, show how you can add using the number line. You set the first addend at the start of the number line. Discuss that you then add the parts of the second addend in jumps. Show the students which jumps were made on the number line. Ask them which number is shown by the mark on the number line. Then practice addition problems in which they make jumps of hundreds, tens and ones on the number line. Remind students that they should first add the hundreds, then the tens, and finally the ones.

Ask students how to split their second addend to show which steps they take in solving an addition problem. Erase the grey boxes to check their answers.

Check that students are able to add to 1,000 via grouping by asking the following questions/giving the following addition problems:

- How do you add via grouping?

- What are the steps you take an adding via grouping?

- How do you solve 460+27= ? and 573+213=?

Students first practice with solving an addition problem using a number line. They must add the second addend in jumps. Next they are asked to add without using a number line.

Discuss with students that it is important to be able to add to 1,000 by grouping (or splitting the second addend) so they can add large numbers easily. Show a selection of addition problems and ask students to solve them using a number line. Show a few different ways in which to solve for the answer on the interactive whiteboard. Next show an addition problem and ask students to determine how to split the second addend. Erase the grey boxes to show the answer.

Students who have difficulty with grouping or splitting the second addend can make use of the number line. Ask them to calculate by drawing every step on their number line. Emphasize that they should jump hundreds first, then with tens, and finally with ones.

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