## Measuring Blocks

Have two or more blocks of different lengths on hand and paper clips to use to measure them. The blocks need to measure a whole number of paper clips whose combined length is less than or equal to 20 paper clips.

Have students work in pairs. Give each pair a block to measure using paper clips. After they have measured their block, say,

Find someone who measured the other block. Ask them how many paper clips long it is. How long will the two different blocks be together if they are laid end-to-end? First try to figure this out. Then put the blocks end-to-end and measure it to check your answer.Ask students to explain how they solved the problem and whether their answer checked out correctly. Even if students added correctly, they may not have lined up the paperclips very carefully and could get different lengths. This is a good opportunity to talk about how important it is to be careful when measuring.

Next, ask the students,

Imagine you put another block end-to-end with the first one you measured. Together, they measure 18 paper clips. How long is the new block? Draw a picture to explain how you know.Ask students to explain how they solved the problem and whether their answer checked out correctly. Finally, ask the students to write equations to represent their work.