Friday Puzzler -- bag of coins

Re: Friday Puzzler -- bag of coins

john Veerkamp

80%

Re: Friday Puzzler -- bag of coins

Larry Barrett

Either .8 or .9, depending on which bag you choose.

So the answer is ... ?

That's correct if

Alex Y

the bag contains 40 pennies, 8 nickels and 2 dimes.

There is another possibility, though, alluded to in Larry's post.

Re: So the answer is ... ?

Larry Barrett

The other alternative is 1 quarter, 2 dimes, 2 nickels, and 45 pennies.

Re: So the answer is

Alex Y

Correct. I was just looking for the last little step. Since you don't know which of those possible bags I hold, in the absence of any other information the natural assumption is that either is equally likely. So the probability that I picked a penny is 85%.