# Subtract Fractions with Common Denominators within Whole

## Elementary / Math / Fractions

To subtract four minus one 8th, which could also be read as taking one 8th from four eighths. We start with our four eighths, and there's two different ways to do this. One, just like it's been for all of your years learning, subtraction, that we can think of it as takeaway, or we could think of it as compare. So to do the takeaway model, we start with four 8s and just like you would think, we simply take it away and what is going to be left. Obviously, it's going to be three eighths. Now, what if we did the compare method? Well, the compare method would look something like this. Four 8 and we're going to compare it to one 8th. So we're trying to see how are they different? So you can see here that the row of four 8s goes that far visually. And you can clearly see where the one 8th goes. So in this method, you would say the difference between four 8s and one eighths by comparison is three eighths. In either case, whether you do the comparison or whether you do the takeaway, it's going to be four eighths. Minus one 8th is three eighths. Notice the denominator stayed the same. One real life example of this would be suppose you have leftover pizza. And four eighths of the pizzas left over. You wake up the next morning, somebody takes one out, what's going to be left? Four out of the 8, not four out of zero. We aren't subtracting the denominators. So four eighths. Minus one 8th equals three eighths.