About this video
Sal identifies the numerator (3, the number on top) and the denominator (4, the number on the bottom) in 3/4. He uses square and round pies cut into 4 equal pieces to show that the denominator is the total number of pieces and the numerator is how many we take.
You'll be able to
- identify the numerator and denominator of a fraction.
- explain what the numerator and denominator mean using a picture.
Key words
- numerator
- The number on top of a fraction; how many pieces we have or use.
- denominator
- The number on the bottom of a fraction; how many equal pieces the whole is cut into.
- three-fourths
- How we read 3/4: three of four equal pieces.
Transcript
We're asked to identify the numerator and denominator in the fraction 3 over 4, or 3/4. So let's rewrite this just so it's nice and big. So let me just write the fraction. So we have 3 over 4, 3/4. Now, they want us to identify the numerator and the denominator.
So the numerator is just the number on top, so the numerator is the 3 right there. And then they want us to find the denominator. The denominator is just the number on the bottom. It's the 4. So if they say what's the numerator? 3. What's the denominator? It's 4, just the number on the bottom.
They could've just called this the number on the bottom. They could've just called this the number on top. Now to think about what this represents, what this fraction represents, you can think of it as three out of four pieces of a pie. That's how I think about it.
So you can imagine, the denominator tells us, what are we taking a fraction out of or how many pieces are there? So let's imagine a pie like this. So we could draw like a square pie. So this is what the denominator represents. This is what the number on the bottom represents.
And then 3 says, we are representing three of those four pieces. So this 3 tells us that out of 4 possible ones, I guess you could think of it, we are using three, or maybe we're eating three. So you can imagine if someone says I ate three-fourths of a pie-- this would be read as three-fourths-- they're eating the blue portion of the pie if we cut it this way.
If we imagine a round pie, it would look like this. Let me draw a round pie. So that is my round pie. Let me cut it into four equal pieces or roughly equal pieces. And if someone says I ate three-fourths of this pie, where the 3 is the numerator, and then the 4, and you'd read that as three-fourths, the 4 is the denominator, they would eat this much of the pie.
They would eat 3 of the 4 pieces. So this is is one piece, this is two pieces, and this is three pieces. So you could imagine the 4, the denominator represents the total number of pieces in the pie, and then the 3 represents how many of those we ate.
Video © Khan Academy, used under CC BY-NC-SA. Watch on Khan Academy. Puzzicle is not affiliated with Khan Academy.