1) In a coin collection, each coin has some combination of the following characteristics:
One of five different colors (white, black, silver, gold, copper)
One of three different shapes (circle, square, hexagon)
One of three letters imprinted on it (A, B, C)
There is exactly one coin with each combination of characteristics. There is one black circle coin with an A on it, one gold square coin with a C on it, and so on.
a. How many coins are in this collection?
I think this is just the Fundamental Counting principle so it is just $5*3*3=45$
b. How many silver coins are in the collection?
I'm confused on this one..
There are $3*2=6$ total outcomes of shapes and letters. Do I just multiply that by $5C1$
c. How many coins have the letter A on them?
Again, I'm confused, is it: $3C1 * 5*3$?
2) Jeff and Caitlin are playing a game. Jeff chooses 4 balls from a bucket of 18 balls numbered 1 to 18. To win, Caitlin must correctly guess the numbers on the four balls.
a. How many ways can Jeff choose four balls?
b. What is the probability that Caitlin correctly guesses the four numbers?
I'm confused about this too. Is it $1/18*1/18*1/18*1/18$