We know that eight plus seven equals 15. Here are the four number sentences for eight, seven and 15. Eight plus seven equals 15. 15 subtract seven equals eight. Seven plus eight equals 15. And 15 subtract eight equals seven.
Here are some number sentences for five, six, and 11. Six plus five equals 11. 11 minus five equals six. Five plus six equals 11. Which number sentence for five, six, and 11 is missing?
If we colour-code the numbers in the same way as the first group of sentences, it helps us to see the pattern. The commutative property tells us it doesn’t matter which order we add the numbers. The answer is still the same. 11, six plus five makes 11. And five plus six makes 11.
We know that the missing number sentence is a minus because there are two addition facts and two subtraction facts for each group of numbers. We already have 11 take away five. So if we switch these numbers, we will get the missing sentence, which is 11 take away six equals five.
The missing sentence is 11 take away six equals five.