Multiples, Factors and Prime Numbers!

Multiples - Any number has a set of multiples.When a number is multiplied by any whole number (integer) the result is called a multiple. For example the first five multiples of 3 are – 3x1 = 3 3x2 = 63x3 = 93x4 = 123x5 = 15

Rules of Divisibility - A number is divisible by

If… Examples

2 The last digit is an even number 12, 134, 36

3 The sum of all digits when added together is divisible by 3

18 1 + 8 = 9

4 The number formed by the last two digits is divisible by 4

732 32 ÷ 4 = 8

5 The last digit is 5 or 0 25, 125, 50

6 The last digit is even and the sum of its digits when added together are divisible by 3.

3, 4263 + 4 + 2+ 6 = 15

7 No divisibility test

8 The number formed by the last three digits is divisible by 8

7, 538 538 ÷ 8 = 67

9 The sum of all its digits is divisible by 9

6, 8316 + 8 + 3 + 1 = 18

10 The number ends in 0 30, 170, 200

Question 14.3 - Use some of the methods for

spotting multiples to decide whether the following numbers are multiples of

2, 3, 4, 5, 6, 8 or 9:

a) 2652 b) 6570c) 2401

Factors - The concept of factor is simply the reverse of multiple.

For example the factors of 12 are – 1 x 12 = 122 x 6 = 123 x 4 = 12

Prime Numbers - Any number that has precisely twofactors, and no more than two, is calleda prime number.

For example the number 13 can only be made by multiplying 1 x 13.

Whereas 12 is a composite number, not a

prime number as 6 x 2 and 3 x 4 = 12.

Counter Activity - To find out if a number is a prime number and not a composite

number you can use counters or draw a diagram. If you cannot make an enclosed pattern with even

columns on each side then the number is a

prime number.

For Example - Thirteen is a primenumber as it cannot be arranged tomake an enclosed pattern, as shownbelow.

However Twelve is a composite numberas it can be arranged to make different enclosed patterns, as shown below.

Can you? List all the prime numbers

between 70and 100.

Hundreds chart

PracticeFor revision and practice of multiples and

prime numbers, the year 3 Mathematics- multiplication skill builder, (F.1-F.11) is available for students, as well as the year 4 Mathematics- prime and composite numbers (A.5) on the IXL website for students (Maths for kids). Students can choose from a variety of mathematics exercises, of different levels and kinds.

References:Math-exercises-for-kids.com-Webmaster:

Laurent Monnot. Retrieved from www.mathsexercisesforkids.com/

You Tube. Prime number song. Prime Time (Maths song) Retrieved from: www.youtube.com/watch?v=pGu9cKL-i8

You Tube. Prime numbers song. Prime numbers- The Sieve of Eratosthenes. Retrieved from: www.youtube.com/watch?v=9m2cdWorlq8.com