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## 3rd grade

### Course: 3rd grade>Unit 5

Lesson 1: Fractions intro

# Cutting shapes into equal parts

Lindsay figures out if 4 pieces of pie are each equal to 1/4 of the pie. Created by Lindsay Spears.

## Want to join the conversation?

• Does a fraction have to be an equal? Why can it not be improper or not equal?
(5 votes)
• By definition, the denominator (the bottom number) in a fraction tells you how many equal sized part will create 1 whole unit. For example: 3/4, the 4 tells you that it take 4 equally sized parts to make a whole unit. The 3 in the numerator tells you that you have 3 parts.

If a shape is cut into unequal portions, then you need to know the size of each portion to determine their fraction of the whole. Then, to find one fraction, you would have to add the fractions together to find the total fraction. You can only add fractions of equal size (denominators match), so there is a process you have to go thru to convert the fractions to a common denominator.

Hope this helps.
(1 vote)
• is 1/4 = to 1/8?
(4 votes)
• 1/8 is actually half of 1/4. Interesting!

That might sound strange because 8 is 2 times 4. But remember we are talking about fractions. If you imagine a pie that has been divided into 4 equal pieces and a pie of the same size that is divided into 8 equal pieces, each piece of the second pie is going to be half the size of the pieces in the first pie.

Think of it another way with only one pie. If you cut the pie into quarters (1/4) so you have 4 equal pieces of pie, and then cut each of those quarter pieces in half, you would have 8 pieces of the pie - each slice is now one eighth (1/8) of the pie. As you cut the quarter (1/4) in half, the eighth (1/8) is half the size of the quarter.

Did that help?
(9 votes)
• From to why didn't she use a pizza as the representation.
(5 votes)
• Pizza or pie, they're both circles. So it doesn't matter which of those we use as a circle representation.
(1 vote)
• what the heck who is this speaker
(2 votes)
• who likes Khan Academy
(2 votes)
• I do!
(1 vote)
• I meant no there are 3/3 of the pie
(1 vote)
• yes each peace of the pie is=to 1/4 of the pie
(1 vote)
• do you work at elliot
(1 vote)
• Why does the shape have to be equal?
(1 vote)
• how do you make a fractor
(1 vote)

## Video transcript

- [Voiceover] Is each piece equal to 1/4 of the area of the pie? So we have a pie, and it has one, two, three, four pieces. So it does have four pieces. So is one of those pieces equal to 1/4 of the pie? Well let's talk about what we mean when we have a fraction like 1/4. The one in the fraction, the numerator, represents a number of pieces. So here, one piece. One piece of pie. And then the four, when we're talking about fractions is always talking about the number of equal size. Equal size pieces. So in this case four equal size pieces. So the question is, is each piece one of four equal size pieces? Let's look at the pie. I think it's pretty clear that these pieces on the end are not equal, they are smaller than the two pieces in the middle. If you love cherry pie, you are not happy about getting this end piece. Because it is smaller. It is not an equal size piece. So yes, each piece is one out of four pieces. But it is not one of four equal size pieces. Therefore it is not 1/4. So our answer is no. No, no, no. Each piece is not 1/4 or an equal share of the pie.