Math CentralQuandaries & Queries


Question from manny, a student:

Suppose you have 6 nickels, 4 dimes, and 2 quarters in your pocket. If you draw a coin randomly from your pocket, what is the probability that

a. You will draw a dime?


I have 6 + 4 + 2 = 12 coins in my pocket. Thus 6/12 = 12 of the coins are nickels, 4/12 = 1/3 of the coins are dimes and 2/12 = 1/6 of the coins are quarters. The task is to select one coin at random.

Suppose that I repeat this experiment a large number of times, maybe 1,000,000 times. I would expect to select a nickel approximately half the time, a dime about a third of the time and a quarter about a sixth of the time. This is one way to look at probability as the proportion of times you expect to obtain the desired result if you repeat the experiment a large number of times. Thus the probability that you select a dime in 1/3.

I hope this helps,

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