Multiplying Fractions

"All You Gotta Do"



Watch this video and learn how to multiply fractions. The song uses example problems to guide students through the steps of multiplying the numerators, multiplying the denominators and simplifying the final product. It includes the real-life example of having to multiply fractions when baking.





Peace y’all. Hope you're feeling alright,
Today you're gonna see fractions get multiplied.
Ok, so here's how it starts:
First you gotta group up the same parts.
The two numerators? Those are on top,
Multiply 'em together
, yeah, but don't stop.
The two denominators, the ones down below,
You've still got to get the product of those
.
There’s your answer: top and bottom,
So simplify by any common factors, if you spot 'em.
14 × 25,
But 1 × 2 is at the top of the list.
Then 4 × 5 leaves you 20,
Then simplify down to 110 there buddy.
And here's a curveball just to have fun,
When you have a whole number, place it over 1
.

Multiply across the top, then across the bottom,
Simplify your answer, yep, now you got 'em.
Multiplying fractions, but you can play it cool,
If you need to multiply 'em this is all you gotta do... (x2)


Ok, now I was hanging out, I had 4 friends next to me,
One of them hands me a cake recipe.
Let me see, uh-oh it serves 10,
But I’m only serving 5, what should I do then?
Since I need 12 of some other fractions,
That means multiplication is the action
.
The original calls for 23
Of a cup of sugar, here's what we do first:
Multiply 23 × 12,
I'm sure by now that you know how to do the math.
That's (2 × 1) ÷ (3 × 2),
Gives you 26, you know what to do.
Simplify that, you're left with 13,
Now you can bake the cake and make sure
That it tastes good and it's not too sweet,
Who'd have thought multiplying fractions can help you eat.

Multiply across the top, then across the bottom,
Simplify your answer, yep, now you got 'em.
Multiplying fractions, but you can play it cool,
If you need to multiply 'em this is all you gotta do... (x2)


Yo, it’s crazy if you think about it... Multiplying fractions is easier than adding or subtracting fractions. Yo DJ Pythagoras, get busy on 'em son.


When multiplying fractions, the first step is to multiply the numerators. The numerators are the numbers on top of the fraction.

Example: 2 5 × 3 4
First, we multiply the numerators to get 2 × 3 = 6


The second step is to multiply the denominators. The denominators are the numbers on the bottom.

Example: 2 5 × 3 4
Multiply the denominators to get 5 × 4 = 20


After multiplying both the numerators and the denominators, it's time to simplify or reduce your product.

Example: 2 5 × 3 4 = 6 20 .
The greatest common factor of 6 and 20 is 2. We divide the top and bottom by 2, which simplifies to 3 10 .


When multiplying whole numbers by fractions, put the whole number into the same format as the fraction by putting it over one.
Example: 1 8 × 2
1 8 × 2 1
We multiply: 1 × 2 and 8 × 1 to get 2 8 .
Simplify 2 8 to 1 4 , and there's your answer.


Fractions have quite a few real-life applications, especially when it comes to cooking! Recipes might call for 1 4 cup of flour or 1 2 tablespoon of vanilla, and if you want to change the recipe to serve a different number of people, you're going to have to multiply fractions.


Serving 5 people instead of 10 means using half as much of each ingredient as the recipe says.
1 2 × 2 3
(1 × 2) / (2 × 3) = 2 6
Simplify to 1 3 .

What if you needed the cake to serve 20 people, not 5 or 10? How much sugar would you need to use then?

When multiplying fractions, what do we do with the numerators?
Multiply them
What do we do with the denominators when we're multiplying fractions?
Multiply those fools!
What do you do once both the numerators and denominators are multiplied?
Simplify by any common factors
What do you do with the whole number when multiplying it by a fraction?
Place the whole number over 1
If a recipe makes 10 servings and you're only serving 5 people, what do you do?
Multiply the amounts in the recipe by 1 2

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