can someone help with this problem 13/15 - 11-20 how do i subtract when bottom is different?

Answer 1

You must make the bottoms the same. In this case, you need to find a number that both 15 and 20 go into evenly. Now 15 x 20 would work, but this is awfully big. Surely something smaller will work.

Look at the multiples of 15 : 15, 30, 45, 60, 75, 90
Now look at the multiples of 20 : 20, 40, 60, 80, 100, 120
Find one that is in both lists.
I found 60 as 15 x 4, and also 20 x 3
So take the first fraction x 4 on both top and bottom
13 x 4 = 52 : 15 x 4 = 60 -- so this will become 52/60
Now take the second fraction x 3 on both top and bottom
11 x 3 = 33 : 20 x 3 = 60 -- so this will become 33/ 60
NOW you can subtract : 52 - 33 = 19
Use the common denominator to get the answer : 19/60

Answer 2

The bottom numbers or denominators need to be the same for addition or subtraction. What you need to do is change both fractions so that you have a common denominator. You could multiply the first fraction by 20 / 20 and the second fraction by 15 / 15. If you did you would get 260 / 300 - 165 / 300. Now you can subtract the top numbers giving you 95 / 300. If you do it this way you will need to simply the fraction, since the top number and bottom number are both divisable by 5. If you do so, you will get 19 / 60.

There is another way to get the bottom numbers, denominators, the same that is called the LOWEST common denominator, LCD. To find the LCD notice both denominators are divisable by 5, so there is no need to multiply either by 5. You can simply multiply the first fraction by 4 / 4, found from the second fraction's denominator, and the second fraction by 3 / 3 found from the first fractions denominator. You will get 52 / 60 - 33 / 60 subtraction top numbers, numerators we get 19 / 60.

Sorry, I had to give you such a long explanation, but if you cannot find a lowest common, lcd, denominator easily. Remember you can still do the problem as I did by multiplying top and bottom of the first number by the whole denominator of the second fraction and multiplying the top and bottom second fraction by the whole denominator.

Answer 3

Common denomintator. You have to get the bottom number to be equal

Problem:
13/15 -
11/20

*4 on 13/15 and that equals 52/60 (multiply the13 and 15 by 4)

*3 on 11/20 and that equals 33/60 (multiply the11 and 20 by 3)

52/60 -
33/60
----------
19/60 tadaa!!

Answer 4

Find the LCD between 15 and 20. Both 20 and 15 divide evenly into 60, so try converting both fractions to 60ths and then subtract.

Answer 5

Do you mean

13/15 - 11/20

The common denominator is 60

52/60 - 33/60 =

Subtract the numerator

19/60

- - - - - - -s-

Answer 6

You have to find a common denominator. Which is 60 so multiply the whole left side by 4 and the whole right side by 3 and get ur answer.

Answer 7

13/15 = 52/60

11/20 = 33/60

52/60 - 33/60 = 19/60

Answer 8

13/15 - 31

now you can write 31 like this 465/15
so
13/15 - 31 = 13/15 - 465/15 = -452/15

Answer 9

(13/15) - (165/15) - (300 / 15) = - 452 / 15 or -30 2/15

Answer 10

Find a common denominator.