Starter Replace the Starter Replace the 05 March

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Starter Replace the ?

05 March 2021 Adding and Subtracting Fractions Objectives : To be able to add and subtract fractions with different denominators To be able to subtract mixed numbers

Adding and Subtracting Fractions Let’s look at two fractions. How can we add these? At the moment we’re stuck, because the fractions have different denominators. We can’t add fifths to quarters. They’re different things. We need to find equivalent fractions with the same denominators.

Adding and Subtracting Fractions I need to think of a number in both the 5 and 4 multiplication tables. I know. 20 is in both the 5 and 4 multiplication tables. This means I can write equivalent fractions with 20 as the denominator. Ug.

Adding and Subtracting Fractions Another (harder) example We need to find a number in both the 7 and 11 multiplication tables, so that when we find equivalent fractions, they both have the same denominator.

Adding and Subtracting Fractions This answer isn’t the best it could be. We don’t like having improper fractions. Let’s convert it to a mixed number. 77 divides into 118 once, with a remainder of 41

Adding and Subtracting Fractions The Golden Rule You can only add fractions with the same denominators. If the denominators are different you need to find equivalent fractions.

Adding and Subtracting Fractions Ex 1. Let’s do some practice. Simplify where possible. 1 5 9 13 17 21 1 4 6 8 2 12 1 3 3 8 7 8 + + 2 8 4 16 2 3 2 5 2 7 5 9 2 6 10 14 18 22 2 10 6 18 3 4 2 5 3 4 + - 2 5 1 6 2 16 2 4 5 8 8 15 3 7 11 15 19 23 3 21 6 11 3 5 2 7 7 11 9 4 + + 2 7 4 22 5 15 3 5 4 7 8 5 4 8 12 16 20 24 1 6 5 7 7 8 4 6 5 9 14 8 + - 4 12 2 14 2 24 1 4 2 7 6 5

Adding and Subtracting Fractions Ex 1. Let’s do some practice. 1 5 9 13 17 21 4 8 8 16 10 12 1 = 2 = 5 6 11 5 10 18 56 72 6 14 15 103 2 31 =1 72 22 6 10 3 18 10 16 18 20 1 8 13 60 = = 3 5 1 6 5 8 9 10 3 7 11 15 19 23 9 21 8 22 = = 3 7 4 11 14 31 16 35 5 20 77 20 8 12 15 77 4 17 =3 20 24 6 12 8 14 = = 1 2 4 7 19 24 22 24 = 11 12 17 63 22 40 = 11 20

Adding and Subtracting Fractions Ex 2. Spot the odd one out. In each row there’s an answer that’s different. Spot it.

Adding and Subtracting Fractions Ex 2. Answers Not a unit fraction Not a mixed number Not a half Not a 15 on the denominator

Adding and Subtracting Fractions 5 QUICK QUESTIONS CHECK Now it’s time to check your learning. You’ll see five questions. They all have a 30 second timer. How many can you get right?

Adding and Subtracting Fractions Question 1 Timer

Adding and Subtracting Fractions Question 2 Timer

Adding and Subtracting Fractions Question 3 Timer

Adding and Subtracting Fractions Question 4 Timer

Adding and Subtracting Fractions Question 5 Timer

Adding and Subtracting Fractions

Adding and Subtracting Fractions What about if we add mixed numbers? We need to convert the mixed numbers to improper fractions before adding. Now let’s find equivalent fractions.

Adding and Subtracting Fractions Ex 3. Let’s do some practice. Simplify where possible. 2 1 5 9 4 1 3 1 5 2 7 + 1 + 3 + 2 1 4 2 10 5 8 2 6 10 2 2 4 2 3 5 8 1 9 - 1 - 2 1 3 1 4 1 7 3 7 11 2 4 9 1 5 4 7 + 2 + 3 3 9 2 15 5 6 2 4 8 12 6 4 3 2 3 + 2 - 3 2 6 3 12 2 3

Adding and Subtracting Fractions Ex 3. Answers 1 5 9 1 4 5 3 2 4 4 10 51 56 = 4 2 5 6 10 2 1 1 1 3 3 8 61 63 3 7 11 2 3 6 1 4 9 5 15 17 42 = 3 1 3 2 8 2 12 0 4 6 5 12 = 2 2 3

Adding and Subtracting Fractions I need the biggest value key! Which colour should I use?

Adding and Subtracting Fractions I need the blue key!

Adding and Subtracting Fractions 5 QUICK QUESTIONS CHECK Now it’s time to check your learning. You’ll see five questions. They all have a 60 second timer. How many can you simplify?

Adding and Subtracting Fractions Question 1 Timer

Adding and Subtracting Fractions Question 2 Timer

Adding and Subtracting Fractions Question 3 Timer

Adding and Subtracting Fractions Question 4 Timer

Adding and Subtracting Fractions Question 5 Timer

Adding and Subtracting Fractions

Problem Solving Three candidates were running for office. One of them got half the vote. Another got two fifths of the vote. What fraction did the third get?

Problem Solving