# Thread: Probability for 15 out of 15 apples to be good when every 10 apple is bad

1. ## Probability for 15 out of 15 apples to be good when every 10 apple is bad

Sub-questions:
Experience shows that 1 in 10 apples is bad. You buy a bag of 15 apples. What is the probability that a) all apples are good, b) all apples are bad? What number of bad apples is most likely to be in the bag?

I really think it is easy to solve...I would really appreciate some help, been stuck for hours

2. ## Re: Probability for 15 out of 15 apples to be good when every 10 apple is bad

So the probability that any one apple is bad is 0.1 and the probability any one apple is good is 0.9. The probability that, out of n apples, all of them are bad is $\displaystyle 0.1^n$ and the probability that all of them are good is $\displaystyle 0.9^n$. The 'most likely number' to be bad is $\displaystyle 0.1n$.