Fun with Fractions

1. Fun with Fractions cummins school dist Adding and Subtracting Fractions

2. Introduction • Fractions are not scary, and can even be fun. • Like most things, people are afraid of fractions because they don’t understand them. • Today we are going to get to know fractions and make friends with them. Adding and Subtracting Fractions

3. Objectives • In this presentation, you will learn the following things: • What a fraction is • What a fraction means • How to add fractions • How to subtract fractions Adding and Subtracting Fractions

4. What is a fraction? • A fraction is made up of two numbers, one on top of the other, divided by a line. • The top number is called the numerator. • The bottom number is called the denominator. • Knowing the names of these numbers is not nearly as important as knowing how to use them. Adding and Subtracting Fractions

5. What does a fraction mean? • A fraction means that something, usually an object or substance, is divided into equal parts. • The bottom number tells us how many equal parts it’s divided into. • The top number tells us how many parts we’re considering. • For instance……. Adding and Subtracting Fractions

6. What does a fraction mean? ½ As the fraction shows, the circle is divided into two equal parts. We are concerned with one part: the blue part. Adding and Subtracting Fractions

7. What does a fraction mean? 1/3 This fraction shows the circle divided into three equal parts. Again, we are concerned with one part, the blue part Adding and Subtracting Fractions

8. What does a fraction mean? This circle is divided into four parts. If we are considering only the blue part, we write ¼. If we are considering both the red and blue parts, we write 2/4, which is the same as ½. Adding and Subtracting Fractions

9. Adding Fractions • To add fractions, your bottom numbers must match. • If you must choose a new bottom number, it must be divisible by both of the old bottom numbers • Once the bottom numbers are the same, you simply add the top numbers • For instance………. Adding and Subtracting Fractions

10. Adding Fractions ½ + ½ =2/2=1 ½ + 1/3 = 3/6 + 2/6 = 5/6 Notice, we used 6 for our bottom number, or common denominator. Both 2 and 3 will divide into 6 an even number of times. Also, whatever number we use to multiply our bottom number, we must also multiply times the top number. In other words, we multiply the 2 in ½ times 3 to get 6, so we must also multiply the 1 times 3 to get 3/6. Adding and Subtracting Fractions

11. Subtracting Fractions • Subtracting fractions works just like adding fractions. • You must make the bottom numbers the same (common denominator). • When the bottom numbers are the same, you simply subtract the second top number from the first top number. Adding and Subtracting Fractions

12. Subtracting fractions So: ¾ - ¼ = 2/4 = ½ 3/8 – ¼ = 3/8 – 2/8 = 1/8 Notice, we had to make our bottom numbers the same (find a common denominator) in the second problem. We used 8 and multiplied 4 times 2 and 1 times 2 to convert ¼ to 2/8. Adding and Subtracting Fractions

13. How Fractions Are Used in Real Life • Fractions are frequently used in any situation where measuring is done. • Cooking frequently requires adding fractions such as ½ cup and 1/3 cup. • Building often requires the addition or subtraction of fractions of inches or feet. Adding and Subtracting Fractions

14. Summary • We have learned that fractions are made of one number (numerator) on top of another number (denominator) separated by a line • The bottom number tells us how many equal parts our object is divided into. • The top number tells us how many of those parts we are concerned with. Adding and Subtracting Fractions

15. Summary • To add and subtract fractions, you must make the bottom numbers match (find a common denominator). • When your bottom numbers match, you simply add or subtract the top numbers. • For practice, work the problems located at the end of the adding and subtracting fractions sections of your workbooks Adding and Subtracting Fractions