About this video
This video works through a table problem about Margo's favorite paintings, sorted by size and dominant color. Using the fact that 1/4 of her large paintings are blue, it fills in the missing totals, then adds the red large and red small paintings to find that 19 of her favorite paintings have red as the dominant color. The key skill is using a known fraction to find a total and then working through a table one blank at a time.
You'll be able to
- use a known fraction of a group to find the group's total
- fill in missing values in a two-way table using row and column totals
- combine counts from two categories to answer a question about a total
Key words
- Fraction of a whole
- A part of a total, such as 1/4, which can be used to find the total when the part is known.
- Two-way table
- A table that sorts data by two categories, such as size and color, and includes row and column totals.
- Equivalent fraction
- A fraction with a different numerator and denominator that has the same value, such as 5/20 and 1/4.
- Missing value
- An empty cell in a table that can be found from the totals and other known values.
Transcript
- [Instructor] Margo classified her favorite paintings hanging in a museum by both size and dominant color. The results are in the table above. We have this table. So we have dominant color. We have large size, small size. We have a bunch of blanks here. I'm guessing we're gonna have to fill some of these out.
Margo found that, okay this is interesting, Margo found that 1/4 of her favorite large paintings were blue. How many of Margo's favorite paintings have red as the dominant color? So we wanna figure out how many of her favorite paintings, whether it's large or small, have red as the dominant color.
So we wanna figure out the total number that have red as the dominant color. And so to figure this out, I think we're gonna have to figure out some of these other blanks. And let's start with the information that they actually gave us. Margo found that 1/4 of her favorite large paintings, so this is her favorite large paintings.
This right over here is the total favorite. This is the total favorite large paintings. 1/4 of this, 1/4 of her favorite large paintings are blue. So 1/4 of this gives us five. So 1/4 of what is equal to five, or five times four is what? Well, this just needs to be 20.
Five out of 20 is the same thing as 1/4. And if we know that, then we can start to fill in some of these other blanks. So if we have a total of 20 large paintings and five are blue, then 15 are going to have to be red, because the red large ones plus the blue large ones is going to add up to 20.
Now, if you have 15 red large and if you have four red small, the total number of red is 15 plus four is 19. So 19 of Margo's favorite paintings have red as the dominant color, 19.
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