Multiplication and Division M O DE LS Multiplication – groups and arrays When we put objects into rows and columns like this we call it an array. Arrays can make it easier to work out how many objects there are in a group. We can 5 use skip counting to help. 2 rows 5 2 rows of 5 is 10 1 How many dots are in the arrays? a b rows of is c rows of is rows of is d row of is 2 How many dots are there? Did you count every dot or did you use a different strategy? Explain how you did it. Operations with Number Copyright © 3P Learning C 3 SERIES TOPIC 53 Multiplication – repeated addition One way to describe multiplication is repeated addition. Look at this array. 5 There are 3 rows. There are 5 dots in each row. We can think of this as: 5 3 rows 5 5 + 5 + 5 = 15 1 How many dots are in the array? a b rows of is rows of is + = + = rows of is c d rows of + + is + = + + + = 2 How many dogs are here? Record using repeated addition. 54 C 3 SERIES TOPIC Operations with Number Copyright © 3P Learning C 3 SERIES TOPIC 54 Multiplication – the × symbol We know that … + means add or join − means subtract = means the same as What does × mean? It means ‘of’. 2 × 5 We have 2 rows of 5 Row 1 5 butterflies Row 2 5 butterflies 2 rows of 5 is 10 altogether. We write this as 2 × 5 = 10 1 How many dots are in the array? Write the number facts. a b 3 rows of × 4 is rows of is = × = c d rows of is rows of is × = × = 2 Colour the right number of squares to match the facts. 2 rows of 5 is 10 2 × 5 = 10 Operations with Number Copyright © 3P Learning C 3 SERIES TOPIC 55 Division – relating multiplication and division We can use the same arrays to make multiplication and division facts. This array shows: 3 rows of 4 is 12 12 counters divided into 3 rows is 4 3 × 4 = 12 12 ÷ 3 = 4 AND 1 Use the arrays to finish the number statements and facts. a 2 rows of 5 is × 10 divided into 2 rows is = ÷ b 4 rows of 2 is c = divided into × = × = ÷ = ÷ d rows is = × = ÷ = 2 Now you can only see part of the arrays. Can you still finish the facts? 4 a 76 C 4 SERIES TOPIC × = ÷ = b × ÷ Operations with Number Copyright © 3P Learning 5 = = C 4 SERIES TOPIC 76 Introducing multiplication – 5 times table 1 11 21 31 41 51 61 71 81 91 Here is a skip counting pattern on a hundred grid. It shows a counting pattern of 5. 1 3 13 23 33 43 53 63 73 83 93 4 14 24 34 44 54 64 74 84 94 5 15 25 35 45 55 65 75 85 95 6 16 26 36 46 56 66 76 86 96 7 17 27 37 47 57 67 77 87 97 8 18 28 38 48 58 68 78 88 98 9 10 19 20 29 30 39 40 49 50 59 60 69 70 79 80 89 90 99 100 Finish each pattern by counting in 5s: +5 a 20 +5 +5 +5 +5 25 +5 b 45 2 2 12 22 32 42 52 62 72 82 92 50 Show × 5 multiplication facts on each number line. a Finish labelling this number line and then show 5 jumps starting from 0: 0 5 20 This is the same as 30 40 × 5 = b Finish labelling this number line and then show 7 jumps starting from 0: 0 5 10 This is the same as 35 45 × 5 = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning DD 11 SERIES TOPIC TOPIC SERIES 3 3 Multiplication facts – 2 times table Counting in 2s, will help you know many times table facts. 1 Complete each pattern by counting in 2s: a 2 4 b 32 34 c 2 12 18 14 18 26 Show how many dots there are in each array by counting in 2s. Then write the times table fact below: c 3 twos × 2 = a 6 twos × 2 = d 5 twos × 2 = 8 D 2 SERIES TOPIC b 8 twos × 2 = e 4 twos × 2 = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning f 9 twos × 2 = D 2 SERIES TOPIC 8 Multiplication facts – 4 times table Practise your 4 times table. 1 Write the multiplication fact for each array: a 3 fours b 4 fours × 4 = d 6 fours × 4 = e 7 fours × 4 = 2 × 4 = f 9 fours × 4 = How many cupcakes are there on: a 4 plates? × 4 = c 7 plates? × 4 = 10 × 4 = c 5 fours D 2 SERIES TOPIC b 3 plates? × 4 = d 9 plates? × 4 = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning e 2 plates? × 4 = D 2 SERIES TOPIC 10 Multiplication facts – 3 times table 4 Label the number line so it goes up in 3s: 0 5 3 Write two turnaround facts for each array. The first one has been done for you. a d 4 × 3 = 12 3 × 4 = 12 × = × = b e × = × = × = × = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning c f × = × = × = × = DD 22 SERIES TOPIC TOPIC SERIES 13 13 Multiplication facts – square numbers A square number is a number multiplied by itself. These arrays show the first 3 square numbers. 1 1 × 1 = 1 2 × 2 = 4 3 × 3 = 9 1 squared = 1 2 squared = 4 3 squared = 9 Here is another way to show square numbers. Look at the array shown on each grid and write the square number multiplication: a b × = 4 squared = 2 c × = × 6 squared = = 7 squared = On this grid, shade the largest square number you can: × = squared = 3 Answer these: a 81 = 18 D 2 SERIES TOPIC squared b 25 = squared Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning c 64 = squared D 2 SERIES TOPIC 18 Division – linking multiplication and division facts Knowing multiplication facts will help with division facts. 6 × 4 = 24 6 rows of 4 is 24. 24 ÷ 4 = 6 1 24 divided into 4 shares is 6. Describe each of these arrays using one multiplication and one division fact: × 4 = 12 a b × 5 = 30 12 ÷ 4 = 30 ÷ 5 = × 4 = 16 c 16 ÷ 4 = 2 This time, you are given part of the array. Complete the array and then write one multiplication and one division fact that matches: a b c 30 D 4 SERIES TOPIC × = ÷ = × = ÷ = × = ÷ = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning D 4 SERIES TOPIC 30 Mental multiplication strategies – doubling and halving We can change the factors of a multiplication question to make it easier. Look at 16 × 3. If we halve the larger factor and double the smaller factor, we make an array on the grid that is the same size. Both arrays have the same amount of squares. Count the squares, are they equal to 8 × 6? 16 × Halve 8 1 3 Double × 6 = Make these problems easier by using doubling and halving. Shade an array for each: a 18 × Halve 3 Double × b 14 × Halve E 3 SERIES TOPIC = 4 Double × 20 48 = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning E 3 SERIES TOPIC 20 Division – division is repeated subtraction Division can also be thought of as repeated subtraction. Look at 30 ÷ 5 = ? This question is asking how many groups of 5 there are in 30. Jump in 5s along the number line and then count the jumps. 6 −5 5 −5 0 1 4 −5 5 10 3 −5 2 −5 15 So, 30 ÷ 5 = 6 1 −5 20 25 30 Show these division facts as repeated subtraction. First label the number lines and then show the jumps. a 36 ÷ 6 = 0 36 b 21 ÷ 3 = 0 2 21 Write a division fact to match these number lines. Show the jumps. a ÷ 0 b 4 ÷ 0 24 = 8 4 SERIES TOPIC 16 20 24 28 = 8 E 12 16 Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning 24 32 E 4 SERIES TOPIC 24 Division – linking multiplication and division facts Knowing multiplication facts will help with division facts. This is because they are opposites. Look at how we can describe this array: 1 6 groups of 4 is 24. 4 × 6 = 24 4 groups of 6 is 24. 24 ÷ 4 = 6 24 divided into 4 shares is 6. 24 ÷ 6 = 4 24 divided into 6 shares is 4. Describe each of these arrays using two multiplication and two division facts: a c 2 6 × 4 = 24 × = × b × = = × = ÷ = ÷ = ÷ = ÷ = × = × = × = × = ÷ = ÷ = ÷ = ÷ = d Draw an array of 6 rows of 3 then describe it with multiplication and division facts. × = × = ÷ = ÷ = Multiplication and Division Multiplication and Division Copyright © 3P Learning Copyright © 3P Learning This is also called a fact family. E E 44 SERIES TOPIC TOPIC SERIES 25 25