Question

A rare item has a 2% chance to drop each time the level boss is slain. Based on this information calculate a. The probability that the item has not dropped at all during 30 attempts. b. The probability that the item drops twice in a row.

Answer 1

I know you have to multiply on this problem

Answer 2

I need to know the number you have to multiply

Answer 3

Let me know what you think NaperVillian

Answer 4

ok, so the problem in a) is asking what the probability is that the item never dropped in 30 attempts. We want to think of each attempt as a single "slot" and we have 30 "slots" because of our 30 attempts

so our entire probability is what is in all those spots multiplied together. In this case, the probability that we don't get the item is 98% each time, so we would do:

.98*30 = 29.4% chance that the item never dropped

Answer 5

Ok there are two answers for this for this problem

Answer 6

part b) is asking what the probability is that the item drops twice in a row. In this case we only have two tries, so we have two "slots" for a result to land. We want both of those to be 2%, so the way we do that is:

2% * 2% = .2*.2 = 0.04

so the answer for the second part is 0.4%

Answer 7

Are you sure that is right for b?

Answer 8

yep. Quite certain. There is a .4% chance. This is different than there being a 4% chance.

Answer 9

Thanks for your help!

Answer 10

You want to be careful for what is meant for part (b): Napervillian's answer is correct *only* when the meaning is "what's the probability of getting two in a row for two *specific* tries in a row (e.g., your next two tries, or tries 10 and 11, etc.). Also, I'm assuming there's a typo in N's answer, it should be .02*.02=.0004 or .04%.

If what is meant is "what's the probability of getting two in a row in some number of tries total (so say the same 30 tries as part (a)), the answer is *very* different. For example, there's about a 0.012 probability (1.2%) of getting two in a row in 30 tries with a .02 (2%) "drop rate".

I'm guessing the question refers to the simpler case, since calculating the general case is much more complex.