All SAT Math Resources
Example Questions
Example Question #41 : Probability
Rolling a four-sided dice, what is the probability of rolling a three times out of four?
Since this problem deals with a probability with two potential outcomes, it is a binomial distribution, and so the probability of an event is given as:
Where is the number of events, is the number of "successes" (in this case rolling a four), and is the probability of success (one in four).
Example Question #1541 : Psat Mathematics
A coin is flipped seven times. What is the probability of getting heads six or fewer times?
Since this problem deals with a probability with two potential outcomes, it is a binomial distribution, and so the probability of an event is given as:
Where is the number of events, is the number of "successes" (in this case, a "heads" outcome), and is the probability of success (in this case, fifty percent).
One approach is to calculate the probability of flipping no heads, one head, two heads, etc., all the way to six heads, and adding those probabilities together, but that would be time consuming. Rather, calculate the probability of flipping seven heads. The complement to that would then be the sum of all other flip probabilities, which is what the problem calls for:
Therefore, the probability of six or fewer heads is:
Example Question #1548 : Psat Mathematics
Set A:
Set B:
One letter is picked from Set A and Set B. What is the probability of picking two consonants?
Set A:
Set B:
In Set A, there are five consonants out of a total of seven letters, so the probability of drawing a consonant from Set A is .
In Set B, there are three consonants out of a total of six letters, so the probability of drawing a consonant from Set B is .
The question asks for the probability of drawing two consonants, meaning the probability of drawing a constant from Set A and Set B, so probability of the intersection of the two events is the product of the two probabilities:
Example Question #52 : Calculating Discrete Probability
Set A:
Set B:
One letter is picked from Set A and Set B. What is the probability of picking at least one consonant?
Set A:
Set B:
In Set A, there are five consonants out of a total of seven letters, so the probability of drawing a consonant from Set A is .
In Set B, there are three consonants out of a total of six letters, so the probability of drawing a consonant from Set B is .
The question asks for the probability of drawing at least one consonant, which can be interpreted as a union of events. To calculate the probability of a union, sum the probability of each event and subtract the intersection:
The interesection is:
So, we can find the probability of drawing at least one consonant:
Example Question #42 : Data Analysis / Probablility
Set A:
Set B:
One letter is drawn from Set A, and one from Set B. What is the probability of drawing a matching pair of letters?
Set A:
Set B:
Between Set A and Set B, there are two potential matching pairs of letters: AA and XX. The amount of possible combinations is the number of values in Set A, multiplied by the number of values in Set B, .
Therefore, the probability of drawing a matching set is:
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 #261 : Data Analysis
There is a bag of marbles that contains thre different color marbles, red, blue and green. There are 12 red, 15 blue marbles and 13 green marbles. There is also a coin with heads and tails that are equally likely. If a person were to randomly select a marble, while flipping a coin, what is the probability that a person will draw a blue marble and see tails on the coin flip?
The probability of selecting a blue marble is the number of blue marbles out of the total number of marbles:
The probability of seeing a tails is one half. Multiplying the probability of drawing a blue marble and seeing tails gives the probability of both events occurring.
The numerator and the demoninator have a common factor of 5 so that this fraction simplifies to:
Example Question #101 : Probability
A drawer contains white shirts, gray shirts, and blue shirts, and no other shirts. If shirts are seclected at random from the drawer, what is the probability that two shirts of the same color are selected?
The probability of choosing the first shirt of a certain color is .
The probability of choosing a second shirt of that color is now because both there are now shirts of that color left and shirts total left in the drawer.
So the probability of choosing both the first shirt AND the second shirt is
* , which equals .
Example Question #101 : How To Find The Probability Of An Outcome
11 cards are placed into a box numbered 5 - 15. If one card is randomly drawn from the box, what is the probabiltiy that a prime number will be on the card?
4/11
2/5
6/11
1/2
3/5
4/11
Possible numbers 5,6,7,8,9,10,11,12,13,14,15 (11 total numbers)
Prime numbers are 5,7,11,13 (4 total prime numbers)
totalnumber of prime numbers/ total numbers in box
Answer = 4/11
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