Is this right?

M

mckriddle

New member
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Sep 8, 2013
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My attempt at this question...

A box contains 11 nickels, 4 dimes and 5 quarters. If you draw 3 coins at random from the box without replacement, how many different 3 coin combinations are there?

20!/(11!4!5!) = 21162960

/3= 7054320


OR

Maybe I am confused on when to use certain formulas, and it's as simple as:

11*4*=220
220 nCr 3 = 1750540


???? or maybe I'm wrong all around...

-Also I have another post on a different question if someone could help me out on that one as well, very lost- trying to get the concepts but I'm pretty much teaching myself.
 
mckriddle said:
My attempt at this question...

A box contains 11 nickels, 4 dimes and 5 quarters. If you draw 3 coins at random from the box without replacement, how many different 3 coin combinations are there?

20!/(11!4!5!) = 21162960

/3= 7054320


OR

Maybe I am confused on when to use certain formulas, and it's as simple as:

11*4*=220
220 nCr 3 = 1750540


???? or maybe I'm wrong all around...

-Also I have another post on a different question if someone could help me out on that one as well, very lost- trying to get the concepts but I'm pretty much teaching myself.
Click to expand...
The question is only asking what distinct combinations could occur. Nothing is being asked about the probabilities of each. All that matters is that there are at least 3 of each coin.

You could have three alike: NNN, DDD, or QQQ

You could have 2 alike: NND, NNQ, DDN, DDQ, QQN, or QQD

Or all three different: NDQ
 
Thank you for clearing that up for me. I kept seeing it as something else- concentrating on the amount of nickels or dimes, which was irrelevant. I have a quiz I have to finish later tonight and I think I'm frying my brain, but this site is helping me understand the concepts more. I appreciate your help.
 
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