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Multiplication Using the Lattice Method including multiplication of decimals by estimation

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What’s It All About? You are going to learn: How to multiply two whole numbers. What skills should you have already? You need to be able to multiply up to 9 × 9 and add single digit numbers.

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Multiplication Using Lattice Demo Calculate 572 × 14 Draw a box. You need three squares across and two squares down. Because 5 7 2 has three digits and 1 4 has two digits …

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Cut each square diagonally in half. Write the numbers to be multiplied around the top and right edges. Use a highlighter pen to highlight every other diagonal stripe. Multiplication Using Lattice Demo 4 5 7 2 1

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Multiply the digits at the top and right of each cell and write the answer in the cell. Multiplication Using Lattice Demo 0 5 0 7 5 7 2 1 4 0 2 0 2 8 0 8 Ten Thousands Thousands UnitsHundreds Tens The digits in each diagonal stripe all have the same place value...

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Add up each stripe. Write the total for each stripe at the end of the stripe. 5 7 2 Multiplication Using Lattice Demo 1 4 0 5 0 7 0 2 0 2 8 0 8 Ten Thousands Thousands UnitsHundreds Tens Now we add up the digits, starting with the units corner...

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Add up each stripe. Write the total for each stripe at the end of the stripe. 5 7 2 Multiplication Using Lattice Demo 1 4 0 5 0 7 0 2 0 2 8 0 8 08 0 8 0 1 1 Always write down your answer... 572 × 14 = 8008

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Question 1 (with answer) Calculate 76 × 21 7 6 2 1 1 5 9 76 × 21 = 1596 1 4 1 2 0 7 0 6 6

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Question 2 (with answer) Work out 152 × 34 1 5 2 3434 0 3 1 5 0 6 0 4 2 0 8 0 5 68 1 1 152 × 34 = 5168

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Question 3 (with answer) Calculate 237 × 14 2 3 7 1414 0 2 0 3 0 7 0 8 1 2 8 0 3 18 3 1 237 × 14 = 3318 1

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Your Turn 1532 × 65 263 × 51 3234 × 97 4 7165 × 4 537 × 45 6103 × 54

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Decimal Multiplication (one decimal number) Calculate 3.5 × 31 First step is identical to whole numbers. 3 5 3 1 1 0 8 3.5 × 31 = 108.5 0 9 1 5 0 3 0 5 5 1 What about the decimal point? 4 × 30 = 120 so the answer is about 120 1 0 8 5

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Decimal Multiplication (two decimal numbers) Work out 15.6 × 7.4 1 5 6 7474 0 7 3 5 4 2 0 4 2 0 2 4 1 1 4 4 5 1 15.6 × 7.4 = 115.44 What about the decimal point? 10 × 8 = 80 20 × 8 = 160 so the answer is more than 80 and less than 160 1 1 5 4 4 1

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Question 4 (with answer) Calculate 9.37 × 1.2 9 3 7 1212 0 9 0 3 0 7 1 8 0 6 1 4 1 1 44 2 1 9.37 × 1.2 = 11.244 What about the decimal point? 10 × 1 = 10 so the answer is about 10 1 1 2 4 4 1 1

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Question 5 (with answer) Calculate 61 × 9.8 9 8 6 1 5 9 7 61 × 9.8 = 597.8 5 4 8 0 9 0 8 8 What about the decimal point? 60 × 10 = 600 so the answer is about 600 5 9 7 8 1

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Question 6 (with answer) Calculate 7.5 × 0.3 7 5 0 3 0 2 2 7.5 × 0.3 = 2.25 0 2 1 5 5 What about the decimal point? 8 × 0.5 = 4 so the answer is about 4 2 2 5

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153.4 × 65 26.3 × 6.1 32.34 × 45 41.65 × 4 53.8 × 4.2 61.03 × 5.6 Your Turn

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