# Adding and Subtracting fractions-3D Animation video

Attention Getting Question:
Have you ever added or subtracted fractions?

Introduction:
A fraction represents how many parts of a whole we have. The number below the fraction bar is called the denominator and represents the number of equal parts in the whole. The number above the fraction bar is called the numerator and represents how many parts we actually have. You can add and subtract fractions easily when the denominators are the same.

Subject:
Imagine a friend and you go to a candy store. Your friend buys a pack of candy that has 10 pieces for you both to share. If you eat one-tenth and your friend eats three-tenths, how much of the pack of candy is gone? We can add those fractions in order to find out the fraction of the pack consumed.

In order to add fractions, first see if the denominators are the same. If the denominators are the same, we can add the numerators of the fractions. Remember, you ate one-tenth of the pack and your friend ate three-tenths of the pack. Both of these fractions have a ten as the denominator. This allows us to simply add the numerators of the fractions together. One part of the pack of candy plus three parts of the pack of candy equals four parts of the pack of candy. This tells us that four parts out of ten parts (or four-tenths) of the pack of candy have been eaten.
We can also subtract fractions easily. Imagine you want to find out how much more of the pack of candy your friend ate than you. We can find the difference between these two fractions by using subtraction. Just like with adding fractions, we have to make sure the denominators are the same when subtracting fractions. Since both of the fractions have a ten for the denominator, we can subtract the numerators as we see them. We have three-tenths of a pack of candy minus one-tenth of a pack of candy. Three-tenths minus one-tenth equalstwo-tenths of a pack of candy, which tells us that your friend has eaten two-tenths more of the package than you.
Another time adding and subtracting fractions is useful is when we are calculating distances. What if a spaceship on the way to Mars has to relay a signal to Earth once it has travelled one-fifth of the distance? Then another signal must be relayed once the ship travelstwo-fifths more of the distance to make sure the ship is taking the correct course. The total distance the ship travels before sending the second signal can be calculated by adding fractions.
Since the first signal was sent after one-fifth of the trip was completed and the second signal was sent after another two-fifths of the trip was completed, we can add the fractions of one-fifth and two-fifths together to find the total. The denominators of both of the fractions are the same, which means we can add the numerators together. In doing so, we find that the ship has completed three-fifths of the trip before sending the second signal to Earth.

Summary:
To summarize, fractions represent how many parts of a whole we have. The numerator is the number above the fraction bar and represents how many parts of a whole there are. The denominator is the number below the fraction bar and represents how many parts make up a whole. When adding or subtracting fractions, first see if the denominators are the same. If the denominators are the same, add or subtract the numerators. Give the solution and keep the denominator the same. You can see that it is easy to add or subtract fractions when the denominators are the same.
Report this Resource
\$2.99
Streaming Video
More products from C3D

Teachers Pay Teachers is an online marketplace where teachers buy and sell original educational materials.