A class of 30 children were numbered from 1 to 30. Here are some of the class:

Their teacher set out a ring of 6 chairs.

Child number 1 sat on the first chair, child number 2 on the second chair, child number 3 on the third and so on going round the circle, up to child number 6. The teacher then asked child number 7 to stand behind child 1, child 8 to stand behind number 2 etc. They continued this pattern until all the children were either sitting on a chair, or standing behind one.

How many people were standing behind each chair?
Who was standing behind child number 3?
What would happen if there were only 4 chairs?