The purpose of this activity is for students to add within 1,000, using any strategy that makes sense to them. The expressions in this activity give students a chance to try different strategies, such as adding hundreds to hundreds, tens to tens, and ones to ones, reasoning with numbers close to a hundred, and using a variety of representations. Students who use base-ten blocks or draw number-line diagrams choose appropriate tools strategically (MP5).

• Select previously identified students to display their work side by side for all to see.
• “Which representations show the same idea or help us find the sum the same way?” (The base-ten blocks and equations show adding hundreds to hundreds, tens to tens, and ones to ones. Both the number line and the words added on the second number to the first number in parts.)

The purpose of this activity is for students to see that they can start adding from the greatest or the least place-value unit and still get the same sum. This understanding prepares students to use the standard algorithm for addition, which calls for starting with the ones.

• Invite students to share their responses.
• Consider asking:
  • “If you were to describe the steps that Andre took to add and the steps that Clare took to add, what would they be?” (Andre added the hundreds, added the tens, added the ones, and then added up all the parts to find the sum. Clare added the ones, added the tens, added the hundreds, and then added up the parts to find the sum.)
  • “How is it that Andre started with the hundreds and Clare started with the ones, but both found the same sum?” (It doesn’t matter the order that we add the numbers. If they’re the same numbers we’ll get the same sum.)