Fractions- adding and subtracting

Fractions are part of a whole. 

1/4 is a larger part than 1/8. 

Adding fractions with the same or "like" denominators. 

Simply add the numerators and the denominator stays the same. 

Numerator

The Numerator is the top number and it tells you how many pieces you have. Here the numerator is 1.

Denominator

The denominator is the bottom number and it tells you how many pieces were possible to make up the whole. Here the Denominator is 2.

Multiple Select

If you were very hungry would you rather share a pizza with 10 friends or with 2?

Which is bigger?

This questions shows us that 1/2 is bigger than 1/10

Multiple Choice

1/2 + 1/2 =

• 2/2

• 1 whole

• 2/4

• ?

Subtracting fractions with the same or "like" denominators

Subtract the numerators and the denominators stay the same. 

What if the denominators are NOT the same??

Denominators MUST be the same to add or subtract fractions! We can handle this!!!!!!

Finding the same or "like" denominator

First you need to look at the two different denominators and find a larger number that they both will divide into evenly. Try to find the Least Common Multiple. Least, meaning the first number you come across that they will both divide into evenly.

1/2 + 1/4 = 

The first number that you come to in the multiples of 2 and 4 that are the same is 4. 2 divides into 4 evenly and 4 divides into 4 evenly. That's the number we want to use as our new common denominator! But if we change the denominators then we have to change the numerators in the same way.......

1/2 + 1/4 = 

• Make new fractions with 4s as the denominators for both fractions

• With 1/2 ask yourself "What did I have to do to the 2 in the denominator to turn it into a 4? (You had to multiply it by 2; 2x2=4)

• Whatever you do to the denominator you HAVE to do to the numerator. We multiplied the 2 by 2 so we're going to multiply the numerator, which is one, by 2 and we get 1x2=2. 

• Our first fraction now looks like this: 2/4

• We don't have to change the second fraction at all because we kept the denominator a 4. 

NOW we can add!

2/4 + 1/4 = 3/4 


Voila!!! YOU DID IT! 

Multiple Choice

What would the common denominator be for 1/10 + 3/4?

• 10

• 40

• 3

• 20

If 20 is our common denominator, what would our new numerators be?

Whatever you did to the denominator. to make it 20, do that to the numerator.

We end up with 2/20 + 15/20 = 17/20

YOU DID IT!!!!

You can now add and subtract fractions!!!!!