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Chapter 7. Fractions. Learning Objectives. Work out fractions of a shaded shape Find equivalent fractions Simplifying fractions Writing fractions of 2 quantities Change improper fractions into mixed numbers Change mixed numbers into improper fractions Add/ subtract fractions
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Chapter 7 Fractions
Learning Objectives • Work out fractions of a shaded shape • Find equivalent fractions • Simplifying fractions • Writing fractions of 2 quantities • Change improper fractions into mixed numbers • Change mixed numbers into improper fractions • Add/ subtract fractions • Multiply fractions • Divide fractions • Problems involving fractions • Fractions on a calculator • Convert recurring decimals into fractions • Convert fractions to recurring decimals
Equivalent Fractions • You must multiply top (numerator) and bottom (denominator) by the same multiply Examples • Write 3 equivalent fractions to ¾
Simplifying Fractions • Divide both top (numerator) and bottom (denominator) by the same number Examples • Simplify the following (a) 25/60 (b) 52/90 (c) Write 42 as a fraction of 80
Top-Heavy Fractions – Mixed Numbers • A top heavy fraction has the top bigger than the bottom • To convert a top heavy fraction into a mixed number divide the top by the bottom • The answer is the whole number bit • The remainder is the new top • The bottom stays the same
Examples Top-Heavy – Mixed Numbers • Change the following into mixed numbers (a) 13/2 (b) 50/3 (c) 100/7 (d) 32/5
Mixed Numbers - Top-Heavy Fractions • A top heavy fraction has the top bigger than the bottom • To convert a mixed number into an improper fraction • New top = whole number × bottom + top • The bottom stays the same
Examples Mixed Numbers – Top-Heavy Fractions • Change the following into improper fractions (a) 41/2 (b) 36/11 (c) 21/7 (d) 83/5
Finding Fractions of Quantities • Divide by the bottom and multiply by the top Examples • 2/5 of 60 • 2/3 of 12 • 1/5 of 30 • 8/12 of 24
Adding/ Subtracting Fractions • Make all fractions top-heavy (if possible) • Make all bottoms the same by multiply • Add the tops • Do not change the bottoms • Make all answers mixed numbers (if possible) EXAMPLES • ½ + ¾ • ½ + 1/9 • 3/8 + ¾
More Examples • 33/10 – 15/8 • ¾ + 2/3 • 11/10 – 5/6 • 34/7 – 25/8 • 33/16 – 25/24
Multiplying Fractions • Make all fractions top heavy if possible • Cancel (divide by the same number) any top and bottom • When no more cancelling can be done multiply the tops and multiply the bottoms EXAMPLES 1. 2/5× 12/21 2. 23/4×12/5 3. 25/8× 31/3 4. 5/6 of 42/7
Dividing Fractions • Make all fractions top-heavy if possible • Turn the fraction after the dividing sign up-side-down and multiply EXAMPLES • 13/5÷ 4/9 • 2/3÷ 5 • 22/15÷ 13/5 • 52/5÷ 12/3
Problems Involving Fractions • Jenny spends 3/5 of her money. If she has £1.40 left how much money did she have to start with? • In an experiment a weight is added to a spring. The spring increases by 2/5. It’s new length is 21 cm, what was it’s length before the weight was added?
Decimals to Fractions • If 1 decimal place put it over 10 • If 2 decimal places put it over 100 EXAMPLES Change the following into fractions • 0.45 • 0.5 • 0.81
Fractions into Decimals • Divide the top by the bottom EXAMPLES Change the following into decimals • ¼ • 4/5 • 108/200
Recurring Decimals • Use dots to show recurring EXAMPLES Change the following into decimals • 1/3 • 1/6 • 6/13