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Example Questions
Example Question #164 : Data Analysis
In a particular high school, 200 students are freshmen, 150 students are sophomores, 250 students are juniors, and 100 students are seniors. Twenty percent of freshmen are in honors classes, ten percent of sophomores are in honors classes, twelve percent of juniors are in honors classes, and thirty percent of seniors are in honors classes.
If a student is chosen at random, what is the probability that that student will be a student who attends honors classes?
First calculate the number of students:
The probability of drawing an honors student will then be the total number of honors students divided by the total number of students attending the school:
Example Question #61 : Discrete Probability
In a particular high school, 200 students are freshmen, 150 students are sophomores, 250 students are juniors, and 100 students are seniors. Twenty percent of freshmen are in honors classes, ten percent of sophomores are in honors classes, twelve percent of juniors are in honors classes, and thirty percent of seniors are in honors classes.
If a student is chosen at random, what is the probability that that student will be a senior student and a student who does not attend honors classes?
First calculate the number of students:
The percentage of seniors that do not attend honors classes is:
Therefore, the probability of selecting a student who is a senior and one who does not attend honors classes is:
Example Question #51 : How To Find The Probability Of An Outcome
There are 4 blue marbles, 5 green marbles, 7 black marbles, and 3 white marbles in a jar. If you reach in and grab out one marble, what is the probabilty of drawing a green marble?
To calculate the probability of an event happening, take the number of ways to draw a green marble (5, because there are 5 possible green marbles to choose) by the total number of ways to draw a marble from the jar (19). Thus the answer is
Example Question #52 : How To Find The Probability Of An Outcome
A fair, six sided die is number with the numbers one through three with each number appearing twice. What is the chance that you roll a two when rolling the die one time?
To calculate a probability, divide the possible ways to get the desire outcome by the total possible number of outcomes. We only care about rolling a 2, which can happen in 2 different ways (because there are two 2s on the die).
Thus we get:
Example Question #53 : Probability
When rolling , what is the probability that the sum of their faces will be ? Reduce all fractions.
To find the probability that two dice sum to seven we need to figure out the total number of ways that can happen. Represent the rolls as an ordered pair, with the first number in the pair corresponding to the first roll, and the second to the second roll. Then all the ways to get a sum of 7 are as follows:
- or 6 different ways.
There are possible outcomes when rolling two dice (6 different ways the first roll could come out, and 6 ways the second roll could come out)
thus the probability the sum is 7 is:
Example Question #53 : How To Find The Probability Of An Outcome
There are , , and in a box. What is the chance of someone drawing out a dish then a spoon, presuming that he or she does not place items back into the box after drawing them out? Round to the nearest hundredth of a percent.
For a probability question like this, first do a sum of the total possible outcomes. For the data given, this is or . Now, the probability of drawing a dish is . After this, there are items in the box. The probability of drawing a spoon after this is .
Now, when two events are sequential like this, the probability of the two together is calculated by multiplying their respective probabilities. Thus, your total probability is or
Example Question #54 : How To Find The Probability Of An Outcome
There are , , and on a shelf. What is the probability of picking a tomato at random? Round to the nearest hundredth of a percent.
For a probability question like this, first do a sum of the total possible outcomes. For the data given, this is or . Now, the probability of drawing a tomato is . Therefore, it is .
Example Question #53 : Probability
A license plate is made up of four capital letters followed by three digits. If a plate is generated at random, what is the probability that it contains only vowels (A,E,I,O,U) for its letters? Presume that letters and numbers can repeat.
Recall that you can calculate the probability of an event by dividing the number of desired outcomes by the total number of possible outcomes. First calculate the total possible outcomes. Think of your plate as having seven slots. The first four can have possible outcomes. The last three can have possible outcomes. (Remember, is a number as well as !)
Thus, you total outcome count is: or
Now, for the vowel-only plates, you will have only choices for your letters. Therefore, you will have . Thus, the probability is:
or , which is:
or
Example Question #56 : How To Find The Probability Of An Outcome
What is the probability that a given random number between and is even and has a hundreds digit that is also even? Round to the nearest hundredth of a percent.
This problem does not need to be as hard as it seems. You need to think of your number like a set of four slots.
Now, based on your description you know that the thousands digit can have , as can the tens digit. The ones digit can only have (since the number has to be even). Finally, the hundreds digit can only have as well. Therefore, you can have a total of or matching numbers. The total amount of numbers that you have are . This is because represents a complete thousand, and so forth for the numbers up to . (You must be very careful when counting like this!)
Thus, your probability is or
Example Question #53 : Probability
are thrown. What is the probability that the sum of their sides will be ? Round to the nearest hundredth of a percent.
When two dice are thrown, remember that the total number of oucomes is or , NOT . (Many students think that it is .)
Now, for the data given, we know that the following pairs will work:
Thus, there are possible outcomes that will work for this data. This means that the probability of this outcome is or .
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