To identify the missing addend in a sum
Give students a number and have them tell you how much must be added to it to make 100. For example, you might say, One hundred is 60 plus___? and let a student complete your statement (40). Repeat with more examples. You might want to pair problems with related answers so that students can use the first answer in each pair to find or check the second.
Part 1 starts with a number that is a multiple of 10, which students use that find the related fact. Part 2 starts with a multiple or 5, which students use to find the related fact. The extension introduce more examples of equations with missing addends that equal 100, using other non-decade numbers.
Let’s find pairs that equal 100. For example, one hundred equals 60 plus __ (40). Let’s see if we can find the missing addends!
When children are enjoying their building of mastery, feel free to repeat. When children are eager for more, try Part 2.
Let’s find more number pairs that equal 100.
As always, when children seem excited for a new challenge, move on.
Let’s keep practicing and find the missing number that gets us to 100.