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Lesson 2: Multiplying whole numbers and fractions

# Equivalent fraction and whole number multiplication problems

Sal relates mixed numbers to whole number/fraction multiplication problem. Created by Sal Khan.

## Want to join the conversation?

• can we do this in mixed fraction form too? and if we can how do we solve it? • yes, we can. As you can see in the last part of the video, it showed 8/3. You can use the 3 and count up with 3, but do not go over 8. 6 so far, right? Now, you convert 6 into 2. (As in 2 wholes). Add the extra remainder.(The fraction of 2 that you did not count). Now, you get 2 2/3!
• I don't really get the whole number times the fraction part. • Say you've got 15/12.
There are fifteen 12ths, or fifteen 1/12ths.

So 1/12 + 1/12 + 1/12... and you keep adding 1/12th onto each other 15 times until you get to 15/12.

Remember 1/12 is just 1 piece of 12 total pieces divided, imagine it as a cake or pizza you've divided into 12 pieces and you count each piece.

So you're only adding the Numerators (top numbers). the denominator (bottom number) never changes, so when you multiply a fraction by a whole number you're only multiplying the Numerator (top number).

You can do it that way... but really the number you're multiplying with is also still a fraction it's 2 wholes so you can write it as 2/1 which is just another way to represent that it's 2 wholes, when you do this multiplying 1 fraction then becomes the same as multiplying 2 fractions cos you've now got 2 fractions.
• how would i multiply 1/4 by 96?
or 1/4 of 96 • Why doesn't Khan ever say at the end something like " So it equals 8/3 which is also the same as 2 2/3"? Or in other word why doesn't he also mention the mixed number form of the answer? • Say you've got 15/12.
There are fifteen 12ths, or fifteen 1/12ths.

So 1/12 + 1/12 + 1/12... and you keep adding 1/12th onto each other 15 times until you get to 15/12.

Remember 1/12 is just 1 piece of 12 total pieces divided, imagine it as a cake or pizza you've divided into 12 pieces and you count each piece.

So you're only adding the Numerators (top numbers). the denominator (bottom number) never changes, so when you multiply a fraction by a whole number you're only multiplying the Numerator (top number).

You can do it that way... but really the number you're multiplying with is also still a fraction it's 2 wholes so you can write it as 2/1 which is just another way to represent that it's 2 wholes, when you do this multiplying 1 fraction then becomes the same as multiplying 2 fractions cos you've now got 2 fractions.Why doesn't Khan ever say at the end something like " So it equals 8/3 which is also the same as 2 2/3"? Or in other word why doesn't he also mention the mixed number form of the answer?A parenthesis is a symbol that looks like this: "(" or this: ")". If you have two parentheses, you can "section off" a part of your expression. In math, you're supposed to perform operations that are inside parentheses first, before you do anything else. For example, in 3 * (4 + 3), you would first add 4 + 3 and then multiply by 3.
In the video, Sal deletes the parentheses because since the only operation in there is addition, you can do it in any order. Parentheses mainly come up when you have multiple operations in one expression, like in the right side of the second equation Sal writes. • Need help. 3 wholes 4/5 times ten  • why does he needs 3 groups of 4 1/3s? • sal, how dose spliting up the numbers help • can we do this in mixed fraction form too? and if we can how do we solve it? 