1. Multiplication byMultiplication by
multiples of 10 and 100multiples of 10 and 100
Objective to multiply numbersObjective to multiply numbers
when 0’s are involvedwhen 0’s are involved

2. StarterStarter
 What is the rule for multiplying aWhat is the rule for multiplying a
whole number by 10?whole number by 10?
 Write down the number and add aWrite down the number and add a
zerozero
 What is the rule for multiplying aWhat is the rule for multiplying a
whole number by 100?whole number by 100?
 Write down the number and add twoWrite down the number and add two
zeroszeros

3. Calculate the following:Calculate the following:
 47 X 1047 X 10
 23 X 10023 X 100
 16 X 10016 X 100
 52 X 1052 X 10
 84 X 1084 X 10
 79 X 10079 X 100
 31 X 10031 X 100
 95 X 100095 X 1000
 58 X 10,00058 X 10,000
 470470
 2,3002,300
 1,6001,600
 520520
 840840
 7,9007,900
 3,1003,100
 95,00095,000
 580,000580,000

4. Main ActivityMain Activity
 Calculate 30 X 40Calculate 30 X 40
 Multiply 3 X 4Multiply 3 X 4
 1212
 How many zeros in the question?How many zeros in the question?
 TwoTwo
 30 X 40 = 120030 X 40 = 1200
 OR 3 X 4 = 12 30 X 4 = 120OR 3 X 4 = 12 30 X 4 = 120
so 30 X 40 =1200so 30 X 40 =1200

5. Another exampleAnother example
 Calculate 40 X 500Calculate 40 X 500
 Multiply 4 by 5Multiply 4 by 5
 2020
 How many zeros in the question?How many zeros in the question?
 ThreeThree
 40 X 500 = 20,00040 X 500 = 20,000

6. Yet another exampleYet another example
 Calculate 700 X 300Calculate 700 X 300
 Multiply 7 by 3Multiply 7 by 3
 2121
 How many zeros in the question?How many zeros in the question?
 FourFour
 700 X 300 = 210,000700 X 300 = 210,000

7. Lets check that we understandLets check that we understand
 200 X 70200 X 70
 60 X 3060 X 30
 800 X 400800 X 400
 2,000 X 302,000 X 30
 14,00014,000
 1,8001,800
 320,000320,000
 60,00060,000

8. The rule-plenaryThe rule-plenary
 We are to multiply two numbers thatWe are to multiply two numbers that
are multiples of powers of tenare multiples of powers of ten
 Firstly we multiply the two digitsFirstly we multiply the two digits
together ignoring the zerostogether ignoring the zeros
 We work out how many zeros in theWe work out how many zeros in the
questionquestion
 We add the number of zeros to ourWe add the number of zeros to our
initial answerinitial answer