"Chances" do have magnitude, though. These sentences are possible, for me:Despite being a plural, "chances" is not something you can count.
It's an idiom meaning "what is the probability .."
If you want a mathematical reply (for example "you have a 20% chance of gaining admission) then it is better to ask more specifically, e.g.Thanks Biffo
Could anybody explain why we must use what instead of how much/many?
I thought that because I wanted to know the amount or extent of my chance I should have used how many/much.