All GMAT Math Resources
Example Questions
Example Question #108 : Arithmetic
In a standard deck of cards there are cards equally split into four suits (clubs, spades, hearts and diamonds).
If the following are true, what are the odds of pulling a diamond followed by a club?
I) This deck contains two jokers with no suit.
II) Three spades have been removed from the deck.
Either statement is sufficient to answer the question.
Both statements are needed to answer the question.
Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.
Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
When calculating probability we need to know the total amount of cards we are pulling from and then also, how many cards from the total are diamonds and how many are clubs.
Since we are given the total amount of cards and the amount cards of each suit from the original question, we see that both statements are needed to calculate the final probability because each statement changes the makeup of our original deck.
I) Gives us an additional two cards to include in our probability calculations.
II) Takes two cards away from our calculations.
Therefore, both are necessary to calculate the correct probability.
Example Question #52 : Discrete Probability
The state fair is holding a raffle for a prize. 500 tickets are put up for sale. What is the expected value of each ticket, assuming all tickets are sold?
Statement 1: Each ticket is sold for $5.
Statement 2: The prize is a new laptop computer.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
Assume both statements are true.
Three things are needed to determine expected value of a ticket:
The price of the ticket, which is given in Statement 1;
The number of tickets sold, which is given in the main body of the problem; and,
The worth of the prize, which is not given anywhere (Statement 2 only identifies the prize; it does not give its value).
The two statements together provide insufficient information.
Example Question #110 : Arithmetic
A state fair is holding a raffle for a laptop computer; there are no other prizes. Ted wants to buy a ticket, but only if its expected value is greater than . Should Ted buy a ticket subject to this criteria?
Statement 1: The laptop has value $800.
Statement 2: The people running the state fair will sell 400 tickets for $5 each.
Note: You may assume all tickets are sold.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Three things are needed to determine the expected value of a game - the probability of a win, the value of a win, and the value of a loss.
Statement 1 provides insufficient information. The statement does not give the number of tickets sold, so no clue as to the probability of a win is given. Also, neither the value of a win not that of a loss is given; the worth of the prize is given, but without the price of the ticket, the value of the win (the worth of the prize minus the price of a ticket) cannot be determined.
Statement 2 provides insufficient information. The statement gives the value of a loss: , the cost of a ticket. The number of tickets sold is given to be 400, so the probability of a win is and that of a loss is ; however, the statement does not give the worth of the prize, which is needed to find the value of the win.
Assume both statements hold. The value of a win is $795—the $800 value of the laptop minus the $5 ticket price. The value of a loss is , as follows from Statement 2. The probabilities are those determined from Statement 2. The expected value of a ticket is the sum of the products of the probability and vlue of each outcome:
which justifies Ted purchasing a ticket under his self-imposed criterion.
Example Question #61 : Discrete Probability
What is the probability that a patient admitted to a certain hospital will have 2 tests performed upon entering the hospital?
(1) A study conducted in the hospital revealed that of the patients will have at least two tests performed.
(2) A study conducted in the hospital revealed that 1 in 5 patients will have 2 tests performed.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
Statements (1) and (2) TOGETHER are not sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
Each Statement ALONE is sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
(1) A study conducted in the hospital revealed that of the patients will have at least two tests performed.
Using the information in Statement (1), we cannot find the probability of patients who have exactly two tests performed upon entering the hospital. The probability given in Statement (1) also includes patients who have more than 2 tests performed.
Therefore, Statement (1) Alone is not sufficient.
(2) A study conducted in the hospital revealed that 1 in 5 patients will have 2 tests performed.
Using Statement (2), we can calculate the probability that a patient entering the hospital will have exactly two tests performed as:
Example Question #111 : Arithmetic
What is the probability that a student guesses the correct answer to each question of a quiz?
(1) There are only 3 questions on the quiz.
(2) Each question has 4 answer choices and only one choice is correct.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
Statements (1) and (2) TOGETHER are not sufficient.
Each Statement ALONE is sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
(1) There are only 3 questions on the quiz.
Using Statement (1), we know that the probability that the student guesses the correct answer to each question is the product of the probabilities of getting each individual question right (getting each question right constitutes independent events). That is:
Pr(Question1 Correct) x Pr(Question2 Correct) x Pr(Question3 Correct)
However Statement (1) Alone is not sufficient.
(2) Each question has 4 answer choices and only one choice is correct.
Using Statement (2), we know that the student has the same probability of getting each question right, which we calculate as:
Pr(Correct Answer)=
Still Statement (2) Alone is not Correct.
Combining Both statements, we find the probability of guessing each correct answer on the quiz as:
Therefore Both statements Together are sufficient but neither Statement Alone is sufficient.
Example Question #111 : Arithmetic
Bronson has a box of 16 markers. The markers are green, red and yellow.
I) The number of green markers is twice the number of red markers
II) There are 4 yellow markers
What are the odds of pulling a yellow marker followed by a green marker followed by a red marker? (Assume no replacement.)
Statement II is sufficient to answer the question, but Statement I is not sufficient to answer the question.
Statement I is sufficient to answer the question, but Statement II is not sufficient to answer the question.
Either statement is sufficient to answer the question.
Both statements are needed to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
To find probability, we need to know the number of each color of marker. Statement I gives us a way to put the number of red markers in terms of green markers. Statement II tells us the number of yellow markers. Using Statement II, we can find out how many red and green markers we have together. Then we would have to use Statement I to find the number of red markers and green markers. Then we can calculate probability. There is no way to do it without both statements.
To recap:
Bronson has a box of 16 markers. The markers are green, red and yellow.
I) The number of green markers is twice the number of red markers
II) There are 4 yellow markers
What are the odds of pulling a yellow marker followed by a green marker followed by a red marker? (Assume no replacement.)
So:
So, we have 4 yellow markers, 4 red markers and 8 yellow markers.
To find the odds of three events, we need to multiply the probability of each event together. We assume no replacement, so for each event, our total number of outcomes decreases by one.
So, the odds are 4 in 105.
Example Question #111 : Arithmetic
Two fair (but possibly, but not necessarily, altered) six-sided dice are tossed, and their sum is noted. Below is a probability table for all possible outcomes.
Which of these choices is a possibility for the numbers on the faces of the dice?
According to the probability table, only an odd number can be rolled. Three of our choices can be eliminated immediately for this reason.
If the dice have on their faces, it is possible to roll a double 6 for a 12; if the dice have or on their faces, it it possible to roll a double 1 for a 2.
This leaves two possibilites. All we need to look at is the probability of rolling a 3 with each choice.
:
A 3 can only be rolled by rolling a 1 on the first die and a 2 on the second. The probability of doing this is
:
Again, a 3 can only be rolled by rolling a 1 on the first die and a 2 on the second. The probability of doing this is
.
The other probabilities can be confirmed to agree with the ones given in the conditions in the problem. This is the correct choice.
Example Question #3211 : Gmat Quantitative Reasoning
Janice has a cooler with bottles of water, cola, and root beer. What are the odds of choosing a water bottle followed by a bottle of root beer?
I) There are 5 times more bottles of root beer than water.
II) There are 75 beverages total in the cooler.
Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.
Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Either statement is sufficient to answer the question.
Both statements are needed to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Janice has a cooler with bottles of water, cola, and root beer. What are the odds of choosing a water bottle followed by a bottle of root beer?
I) There are 5 times more bottles of root beer than water.
II) There are 75 beverages total in the cooler.
To calculate probabilty, we need to know the number of desired outcomes and the total number of outcomes.
II) gives us the number of total possible outcomes.
I) gives us a clue about the number of desired outcomes, but it is insufficient to find the actual number of root beers and waters.
Therefore
Neither statement is sufficient to answer the question. More information is needed.
Example Question #61 : Discrete Probability
A coin is flipped five times. What is the probability of it landing tails exactly three 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).
Thus, the probability of three heads in five flips is:
Example Question #61 : Dsq: Calculating Discrete Probability
What is the probability of drawing a card that is blue or has a value of nine from a deck of mystery cards?
1) The probability of drawing a blue card is , and the probability of drawing a nine is
2) The probability of drawing a blue nine is
Statement 2 alone is sufficient.
Either of the statements is sufficient.
Together the two statements are sufficient.
Statement 1 alone is sufficient.
Neither of the statements, separate or together, is sufficient.
Together the two statements are sufficient.
The probability of either of two events happening, the union, is given by the formula:
Because we are not told that drawing a blue and drawing a nine are mutually exclusive events, we must know the probability of the intersection, of drawing a blue nine.