You deal with whole numbers and money every day so we suggest starting with Unit 2 Practice first if these initial practices seem difficult. You memorized many rules about adding and subtracting fractions, and we are quickly going to more “rules” into common sense.
“Comparing apples and oranges” is a common phrase stating you cannot compare 2 things that are not alike. Young children start by adding 2 apples and 3 apples to find there are 5 apples. Similarly, you could add 2 orange wedges and 3 orange wedges to get 5 orange wedges. If both oranges had 8 total wedges then you may have just added 2 eighths and 3 eighths.
The biggest mistake to avoid
When we add and subtract, we have to add the same thing. Consider adding a half and a quarter.
The mistake is to add 1 half and 1 fourth and get 2 sixths. When you see it in words, hopefully it makes this mistake more obvious. You can also think about money: half a dollar is $0.50 or two quarters. So, when you add one half and one quarter it equals three quarters ($0.75).
We started with the big idea that is easy to make mistakes so that you could practice with this in mind. We really like this simulator so you can get used to building fractions and mixed numbers with different denominators.
In pizza terms, you can remember that one quarter of a pizza plus one half of a pizza is still three quarters of a pizza. This video will give you another resource for thinking about adding fractions.
Multiplying Fractions
This video explains how to multiply fractions. (You may want to start a “cheat sheet” with an example of each operation so you can become fast and accurate with these fraction calculations.)
Progress Check
Practice: This worksheet has subtraction of whole numbers, fractions and decimals. Click here when you are ready to check your answers.