Examples of what pupils should know and be able to do
Recognise that a whole number is divisible by:
- 3 if the sum of its digits is divisible by 3;
- 6 if it even and also divisible by 3;
- 8 if half of it is divisible by 4, or the last three digits are divisible by 8;
- 9 if the sum of its digits is divisible by 9;
- 25 if the last two digits are 00, 25, 50 or 75.
Probing questions
Can you give me an example of a number greater than 500 that is divisible by 3?
How do you know whether a number is divisible by 6? etc
Can you give me an example of a number greater that 100 that is divisible by 5 and also by 3?
Is there a quick way to check whether a number is divisible by 25?
What if pupils find this a barrier?
Use the number grid ITP - Zip file (462Kb) or shade a 1-100 grid to help pupils investigate rules of divisibility.
Ask pupils to record the rules in their own way, then set challenges for pupils to sort a set of given numbers into those divisible by 3, 5, 9, 25, etc.
Revisit regularly.
<< Previous Step | Next Step >>