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Probability - Problem 1
MA, Stanford University
Teaching in the San Francisco Bay Area
Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts
Have you guys have you ever seen those magic TV shows where they have a guy on the street with deck of cards and he like can magically pull out whatever card he wants to? Let’s talk about what’s going on, what’s the probability that you can pull out any card you want to?
In that case for this problem we are looking at aces. What’s the probability of pulling an ace out of a deck of cards on your first try ignoring jokers? Okay remember the way to set up a probability is the probability of an event happening I’m going to write that as p of getting an ace is equal to the number of successful outcomes on top, number of possible outcomes on the bottom.
Well think about what you know about a deck of cards, there are four aces anyone of those aces would be a successful outcome. The possible outcomes are 52 because there’s 52 cards in a deck. So this is going to be my final answer but I want to rewrite it, I could reduce that fraction to be 1/13, that’s one way to write your answer because that’s a number between 0 and 1. You could also grab a calculator and do 1 divided by 13 and get the decimal 0.077, that’s an equivalent way to write your answer or as a percent I could write it like this 7.7%. The way I got that was by moving my decimal place to over two spots.
All of these three things are the same correct answer to this problem. This is also kind of correct but it’s not a reduced fraction. So make sure you read the directions carefully or talk to your teacher and find out what kind of answer you should be giving to your probability problems so they be decimals percents or fractions.
You don’t want to get marked off on your homework for something silly like forgetting to change what your answer looks like.
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Sample Problems (3)
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Problem 1 6,162 views
What's the probability of pulling an ace out of a deck of cards on your firs try? (Ignore jokers)
Problem 2 4,945 views
What's the probability of rolling a die and getting an even number?
Problem 3 4,765 views
A sock drawer has 4 pairs of white socks, 3 pairs of tan socks, and 3 pairs of black socks. If you pull one pair, what's the probability that it will be white?