# Multiplication by multiples of 10 and 100 Objective to multiply numbers when 0’s are involved.

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Multiplication by multiples of 10 and 100 Objective to multiply numbers when 0’s are involved

Starter What is the rule for multiplying a whole number by 10? Write down the number and add a zero What is the rule for multiplying a whole number by 100? Write down the number and add two zeros

Calculate the following: 47 X 10 23 X 100 16 X 100 52 X 10 84 X 10 79 X 100 31 X 100 95 X 1000 58 X 10,000 470 2,300 1,600 520 840 7,900 3,100 95,000 580,000

Main Activity Calculate 30 X 40 Multiply 3 X 4 12 How many zeros in the question? Two 30 X 40 = 1200 OR 3 X 4 = 12 30 X 4 = 120 so 30 X 40 =1200

Another example Calculate 40 X 500 Multiply 4 by 5 20 How many zeros in the question? Three 40 X 500 = 20,000

Yet another example Calculate 700 X 300 Multiply 7 by 3 21 How many zeros in the question? Four 700 X 300 = 210,000

Lets check that we understand 200 X 70 60 X 30 800 X 400 2,000 X 30 14,000 1,800 320,000 60,000

The rule-plenary We are to multiply two numbers that are multiples of powers of ten Firstly we multiply the two digits together ignoring the zeros We work out how many zeros in the question We add the number of zeros to our initial answer

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