If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# 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?

• how would i multiply 1/4 by 96?
or 1/4 of 96
• You first make 96 into 96/1 then multiply strait across which makes 96/4.Now divide 96 and 4 which makes 14. 1/4x96=14 :).
• 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?
• He's not try'in to confuse people. It's just that some people act like that to get the answers. That's a fact.
(1 vote)
• Need help. 3 wholes 4/5 times ten
• 3 4/5 x 10
= 19/5 x 10
= 38
• 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.
• why does he needs 3 groups of 4 1/3s?
• What's a parenthesis? He said that in 1.44 - 1.54 from the video.
• 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.
• Why did you use the method that you did?
• Just so you have somewhat of an understanding on how you can view equivalent fractions by using multiplication problems.
• what is 1 third plus 2 eigths
• 1∕3 + 2∕8

Begin by simplifying the fractions.
1∕3 + 2∕8 = 1∕3 + (1 ∙ 2)∕(4 ∙ 2) = 1∕3 + 1∕4

Then write the fractions so that they have the same denominator.
1∕3 + 1∕4 = (1 ∙ 4)∕(3 ∙ 4) + (1 ∙ 3)∕(4 ∙ 3) = 4∕12 + 3∕12