There are 10 light bulbs, 6 are non faulty and 4 are faulty. You choose 3 lightbulbs from 10. The first question is how many different ways can you choose 3 bulbs from 10 and this I know which was 10C3. But after that the question asks "Assuming the 3 bulbs from 10 are chosen at random"
A. What is the probability of choosing exactly one faulty bulb? Now the markcheme says to use counting principles but cant you only use counting principles when all the outcomes are equally likely? Because choosing 3 light bulbs that are non faulty doesn't have the same probability as choosing 3 light bulbs that are faulty? Im confused as to how they are saying the outcomes are equally likely, I know how to solve the question if the outcomes are equally likely so you dont need to help me do that could someone just explain to me why the outcomes in the sample space of choosing 3 lightbulbs in this specific 10 are all equally likely. Thanks