Year 3 Investigation – Multiply by 5

**Investigation Multiply by 5.**

Amir looks at the following number sentence below:

He says: ‘I know that the answer to this is incorrect without even having to work out the answer.’

How can he tell immediately that the answer is wrong?

Explain how you know.

Answer:

Any number that is multiplied by 5 always has the ones column with either a 5 or a 0 (or the number will end with either a 5 or a 0).