Divisibility Tests - PowerPoint PPT Presentation

Divisibility Tests

How can you tell quickly whether a number can be divided exactly by another?

A number is DIVISIBLE by another number

if there is no remainder after division.

The result after division is a whole number and the remainder is zero.

eg 36 divided by 12 is 3, so we say

“36 is divisible by 12”

Divisibility by 2:

Numbers that end in 0, 2, 4, 6 or 8 can be

divided exactly by 2.

They are said to be divisible by 2, and are also

called EVEN numbers.

Numbers that are not even are called ODD.

Divisibility by 3:

To test for divisibility by 3 (without actually

doing the division),

add all the digits together

and if the sum is divisible by 3, then the

original number is too.

This is a “divisibility test for 3”.

Divisibility by 4:

A number is divisible by 4 if its last two digits

can be divided by 4.

Can you explain why this is so?

Divisibility by 5:

How can you tell by looking at a whole number

if it can be divided by 5?

State a “divisibility test for 5”.

Divisibility by 6:

A number that can be divided by 6 needs to be

able to be divided by both 2 and 3.

Now state a “divisibility test for 6”.

Divisibility by 11 and others:

Find out about other “divisibility” tests

– egby 11.

Let’s test a number eg 120

2? Yes, because it ends in 0, so is even

3? Yes, because 1 + 2 + 3 = 6, which of course

is divisible by 3!

4? Yes, because 20 can be divided by 4

5? Yes, because it ends in 5 or 0.

6? Yes, because it can be divided by 2 and

by 3.

Test all the numbers on this page for

divisibility by 2, 3, 4, 5, and 6.

Remember some may be divisible by more than

one of these numbers and some may not be

divisible by any of them!

240 27 256 81

711 400111

• 9123 108

50 343180

Write down your answers!