This is an important skill for the following reasons: you need to be able to arrange numbers in ascending and descending order, and you need to be able to understand what is meant by the magnitude (size) of a number.
Of course, when learning maths you'll realise it's mostly about numbers. However, there are also mathematical terms that you won't come across elsewhere and these need to be understood in order to complete some calculations. As you move up the curricula at school, be prepared to learn new words relating to maths all the time.
See if you can get a perfect score in this easy 11-plus quiz. If you think you've sussed it, move onto the next quiz ~ Compare and Order Numbers - Medium ~ and further improve your maths knowledge. Or, if you need more practice, try Compare and Order Numbers 2 (Easy).
Good luck!