Converting Fractions to Decimals Lesson 5.2 AMSTI 2006

Video Lets watch a video to preview how to convert fractions to decimals, the Egyptian way!

Converting Fractions to Decimals To convert a Fraction to a Decimal manually, follow these steps: Step 1: Find a number you can multiply by the bottom of the fraction to make it 10, or 100, or 1000, or any 1 followed by 0s. Step 2: Multiply both top and bottom by that number. Step 3. Then write down just the top number, putting the decimal place in the correct spot (one space from the right for every zero in the bottom number)

Method #1: Converting with Proportions Example # 1: Express 3/4 as a Decimal Step 1: We can multiply 4 by 25 to become 100 Step 2: Multiply top and bottom by 25 3 = 75 4 100

Example # 1 continued…. Step 3: Write down 75 with the decimal place 2 spaces from the right (because 100 has 2 zeros); Answer = 0.75 Can you explain what we just did? Try to express ¼ as a decimal using method # 1.

Method #2: Convert by Dividing Example #1: to write 5/8 as a decimal, we need to calculate 5 ÷ 8: 0.625 8 √ 5.000 So = 0.625 as a decimal. Try this example: write 4/5 as a decimal using division (method #2).

Remember… To change a fraction to a percentage follow the rules for fraction to a decimal and then multiply by 100. Or use the magic square! Cross multiply  Part Variable Whole 100

Lets Practice!! We are going to use this website to fish out some fractions and decimals. Lets see how well you understand this lesson. Go to www.iknowthat.com Select “Math” in the left margin Select “Fishy Fractions” Select “Fractions and Decimal Match”