Compute with Mass

For this activity, students work in pairs with a two-pan balance and a set of masses. To introduce the activity, use the display of the Make It Balance page in the Student Activity Book to demonstrate the example. Point out the first number sentence.

Record this number sentence on the Another Number Sentence line.

Record 20 + 10 + 10 + 5 = 20 + 20 + 5 on the Combined Number Sentence line.

Have students work in pairs for Questions A–E on the Make It Balance pages. Students place masses that match the first number sentence on one side of the balance and find another set of masses that will balance the pans. For each question, students write a second number sentence with the same sum as the first number sentence and then combine the two number sentences into one true statement.

For Questions F–I, students take turns challenging each other to show the same total mass using a different combination of standard masses. They write their number sentences on the Make It Balance page and combine the two number sentences to make a true statement with more than one addend on either side of the equal sign. Extra spaces are provided for students ready for additional practice.

Assign the True or False Statements page in the Student Activity Book to give students more practice looking at different partitions of a number connected by an equal sign. Upon completion, ask students to explain how to change any false statements in Question 1 to a true statement.