Adding and Subtracting Fractions
By: Marwa and Jaymie
Subtracting Fractions
First Method- regular fractions
First, all you do is list the multiples of each denominator... 5,10,15
3,6,9,12,15
As you can see the common denominator is 15,
Now that we know the common denominator we have to multiply
5 multiplied by 3 gives us 15 and 3 multiplied by 5 gives us 15
remember anything you do to the denominator you HAVE to do to the numerator
3 x 3 2 x 5
____ -- ____
5 x 3 3 x 5
so our fractions are now... 9/15 - 10/15
now that we have the denominators the same we can simply subtract the numerators
9-10=1
Answer= 1/15---remember the denominator always stays the same.
Second Method- improper fractions
First, we find the common denominator
5,10
2,4,6,8,10
As you can see 10 is the common denominator,now its time to multiply
5 multiplied by 2 is 10 and 2 multiplied by 5 is 10
remember anything you do to the denominator you must do to the numerator
15 x 5 10 x 2
_______ --- ________
2 x 5 5 x 2
our fractions are now.... 75/10 - 20/10
After that we simply subtract the numerators
75 - 20 = 55
Answer: 55/10
In this example the answer can be reduced and since this is a improper fraction we have to turn it into a mixed number, so we have to see how many times the denominator goes into the numerator, 10 goes into 55 , 5 times so 5 will be our whole number and the remainder is 5 and the denominator stays the same so it will be 10 so it will look like this .........
Final Answer: 5 5/10
Whole #=5
remainder =5
denominator=10
Third Method- mixed numbers
First, we have to turn each mixed number into an improper fraction
and to do that we have first multiply the whole number and the denominator and then add the numerator so 1 x 6 + 11 = 17/6 and 2 x 3 + 2 = 8/3 ---- remember the denominators always stay the same
Now that we have the improper fractions we must find the common denominators
6,12
3,6
As you can see 6 is the common denominator, 6 x 1 is 6 and 3 x 2 is 6 so...
17 x 1 8 x 2
______ ---- ______
6 x 1 3 x 2
our fractions are: 17/6 - 16/6
now that we have that we can simply subtract the numerators
17-16=1
Answer: 1/6