100’s

Chris Clements

Properties of Number

Divisibility tests

4’s25’s

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Learning Objective:

<Steps to success>

Divisibility tests help usidentify if a whole number

is in a specified times table

e.g. Is 1272 in the 4 times tables (is it a multiple of

4)?

Divisibility Tests

In this lesson you will learn divisibility tests for

multiples of 4, 25 and 100.

Lets see if we can find a divisibility test to see if 1272 is

in the 4 times tables (is it a multiple of 4)?

Divisibility Tests

Can you remember learning a divisibility test for multiples of 2?

All multiples of 2, are even and end with a 0, 2, 4, 6 or 8.

Knowing this will help find a divisibility test for multiples of 4.

Any ideas?

Look at the first 10 multiples of 2.

Every other number is a multiple of 4

2, 4, 6, 8, 10, 12, 14, 16, 18, 20

What do we know so far?• all multiples of 4 are even

• if you half a multiple of 4 the answer is always a multiple of 2

•100, 200, 300.. are all multiples of 4How do we know the last point is

true?Why is it important?

It is important to make the divisibility test less complicated.

Look;If we look at the last 2 digits of any given whole number e.g.

1272It’s even (so it is

definitely a multiple of 2)

If we half it; It’s still evenso it must

be a multiple of 4

Divisibility test for multiples of 4 Look at the last 2 digits; are they

even; if so when you half them are they still even.

Divisibility Tests

Give it a go;

Do you know a divisibility test for multiples of 25?

Divisibility Tests

Lets have a look at the first eight multiples of

25. 25, 50, 75, 100, 125, 150, 175, 200

What do you notice?

The tens and unit digit end in; 00, 25, 50, 75 and so on…

25, 50, 75, 100, 125, 150, 175, 200

Lets find multiples of 25 by doing the divisibility test; ends with a 00, 25, 50, 75.

Divisibility Tests

Do you know a divisibility test for multiples of 100?

Divisibility Tests

Lets have a look at the first eight multiples of

5. 100, 200, 300, 400, 500, 600, 700, 800

What do you notice?

The last two digits are 00. So the test could be whole numbers

ending in 00.

100, 200, 300, 400, 500, 600, 700, 800

Lets find multiples of 100 by doing the divisibility test whole numbers

ending in 00.

Divisibility Tests

Divisibility tests for multiples of 4, 25 and 100

1) For multiples of 4; are the last 2 digits even; if you half the last 2 digits is the answer still even.

2) For multiples of 25; whole numbers ending in 00, 25, 50, 00.

3) For multiples of 100; whole numbers ending in 00.

Divisibility tests

Steps to success

Activity

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Plenary

A number sequence starts 25, 50… which of the following numbers will be in the sequence?

All numbers that endin 4 are multiples of 4

Is this true?Explain if you know