# Skye has eight loonies, ten toonie's, and six quarters in her pocket. She needs two loonies for a parking meter. She reaches into her pocket and pulls out two coins at random. Determine the...

Skye has eight loonies, ten toonie's, and six quarters in her pocket. She needs two loonies for a parking meter. She reaches into her pocket and pulls out two coins at random. Determine the probability that both coins are loonies.

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steveschoen | College Teacher | (Level 1) Associate Educator

Posted on

Probability = # favorable outcomes / # total outcomes

For this, the total outcomes are the total number of things you can pick, 8+10+6 = 24.  When you pick the first time, there are 8 loonies.  These are the favorable outcomes.  So, P(a) = 8/24 = 1/3

Now comes the tricky part.  Assuming you need to the two loonies for the parking meter, I would assume you aren't putting the first loonie back, keeping it out of your pocket.  Why do we need to make sure of this?  For the second one, if you put it back, you have 24 to choose from.  If you don't, you are choosing from 23 total coins.  I am assuming you are keeping it out.  So, we are choosing from 23 coins.  There are still 7 loonies in there.  So, that probably would be P(b) = 7/23.

The overall probability for both picks would then be the product of these two.  Or, P(a and b) = 1/3 * 7/23 = 7/69

prathyuk99 | (Level 1) eNoter

Posted on

Probability of first coin being a loonie multiplied by the probability of the second coin being a loonie.

So, 8/24 * 7/23

8/24: eight loonies out of 24 total coins

7/23: 7 remaining loonies out of 23 total remaining coins

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