This document discusses multiplying numbers by multiples of 10 and 100. It explains that to multiply a number by 10, you write down the number and add a zero, and to multiply by 100 you write down the number and add two zeros. It then provides examples of multiplying various numbers by 10, 100, 1000, and 10,000. It emphasizes that when multiplying numbers with zeros, you first multiply the digits ignoring the zeros, then add the appropriate number of zeros based on how many are in the original numbers.

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