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# Multiplying positive and negative fractions

See examples of multiplying and dividing fractions with negative numbers. Created by Sal Khan.

## Want to join the conversation?

• So if you add a negative to a negative, you get more negatives? Because I thought a negative plus a negative is a positive. I'm really confused
• Addition an subtraction can be seen as movement along the number line. Subtraction means move to the left of the line, while addition means move to the right. While the negative symbol on a number means move the opposite direction as you normally one.

Imagine this as a number line:
-5, -4, -3,-2,-1, 0 -1, 2, 3, 4, 5

if you have (-2) - 2 =?
You start at -2, move to the left two places, and your answer is -4.
If you have 5 - 7 =?
Then you start at 5, move to the left 7 places which places you at -2

If you're given 1 + (-2)=?
You start at 1, and with addition you usually move to the right, but it's a negative, or opposite to, so you move to the LEFT instead, ending at -1.
• At , Sal. says that we cannot simplify 21/20 anymore. Can't we turn it into a mixed number, say 1 1/20?
• Good question! Yes, we can turn into a mixed number, but it is simplified as a fraction. numerator and denominator do not have any common factors other than 1.
• At , why does Sal say that you can't simplify -21/20? Can't you simplify it to
-1 1/20? Or is it -21 over +20? :(
• First of all you can't simplify one part of the fraction when you want to simplify a fraction you must do it for both numerator and denominator and in this fraction you can't simplify it any further because there isn't any common factor between them (21)=3*7 (20)=4*5 hopefully this helps you
(1 vote)
• 5/9 X 3/15 . I don't understand the step where they both were divided by 15 in the above video.
• They were both divided by 15 because 5 times 3 is 15 and 9 times 15 is 135. Since both numbers had a GCF (Greatest Common Factor) of 15, Sal divided by 15 and received an answer of 1/9 because 15 divided by 15 is 1 and 135 divided by 15 is 9.

Unless you were looking for some other answer I suppose?
• What would happen if you multiply a negative fraction and a positive fraction?
• If you multiply a negative by a positive you will always get a negative no matter if there is a decimal, fraction or whole number
• Can someone help I do not get this.
At all
• How are you guys and girls? Are you guys strangers or by people that I know!
:) but mostly absotually :(
• How would you draw a model for -7/10?