I'd say your english could do with a brush up too.
Maths is a very important part of their testing, so assume it's important for the job itself. Being able to multiply or divide in your head is pretty essential for the numeracy tests. You should get a piece of paper and pencil if you need to write it down to work it out. However, speed is also a deciding factor, so try not to take too long on each question, skip to an easier one if need be.