Learn about Addition and Subtraction Facts of Whole Numbers Let’s cover addition and subtraction facts. We are given the numbers 5, 6 and 11 and we are told that they are a fact family. We need to form two addition and two subtraction facts with these three numbers. We are given 5, 6 and 11. We need to remember that addition and subtraction are inverse operations. I can undo one by doing the other. What that means is I can undo addition by subtracting or by subtraction of the addend; addend as what’s being added and I can undo subtraction by adding what was subtracted which is called the subtrahend. There are just two terms to remember. Let’s get back to the facts. The fact is if 5, 6 and 11 are a fact family, we can arrange them to form the facts that we’re looking for. Let’s go for the addition facts first. The addition fact we know is 5 + 6 = 11. I’m writing it differently, 5 + 6 will total 11. This is the first addition fact. We know that addition is a commutative property, so if 5 + 6 gives us 11, 6 + 5 will give us 11 as well or 6 when added to 5 will give us 11; this is the second addition fact. Let’s switch to the subtraction facts. We are given the numbers 5, 6 and 11. What do we know? We know that 5 + 6 = 11. Since addition and subtraction are inverse operations, what do we know? We can also say that if I take away 5 from both sides, 6 becomes 11 - 5. All I did was subtracted 5 from the left and 5 from the right, so 6 will become 11 - 5. This can be shown by 11 – 5 = 6. This is the first subtraction fact. The second piece that we need to remember is if 5 + 6 = 11 then 6 + 5 = 11 as well. In each case, I can leave 5 on the left side. Let’s subtract 6 from both, so I get 5 = 11 - 6. This is the second subtraction fact, 11, when I subtract 6 from it gives me 5; this is the second subtraction fact. Quickly recapping what we’ve learned. Addition and subtraction are inverse operations. If we look at a fact family which is 5, 6 and 11, we can use these and undo addition by subtraction and undo subtraction by adding the numbers back. If we are looking for addition facts, we know 5 + 6 = 11, that’s one fact and because they’re commutative, 5 + 6 = 11 means 6 + 5 = 11 as well. Similarly, if we know 5 + 6 = 11 then 6 becomes 11 - 6, that becomes the first fact of subtraction and if 11 - 5 is 6 then 11 - 6 is 5 which is the second subtraction fact.