All GMAT Math Resources
Example Questions
Example Question #1092 : Data Sufficiency Questions
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.
Either statement is sufficient to answer the question.
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.
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 #112 : Arithmetic
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 #111 : Arithmetic
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
Together the two statements are sufficient.
Neither of the statements, separate or together, is sufficient.
Statement 1 alone is sufficient.
Either of the statements is sufficient.
Statement 2 alone 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.
Example Question #1101 : Data Sufficiency Questions
Twelve indepent trials are run, testing the reliability of a new engine part. What is the probability that the part will fail less than half of the time?
1) The probability that the part will fail three times in six trials is
2) The probability of the part not failing is
Either of the statements is sufficient.
Statement 2 alone is sufficient.
Together the two statements are sufficient.
Statement 1 alone is sufficient.
Neither of the statements, separate or together, is sufficient.
Either of the statements is sufficient.
Since this probability question deals with successes and failures, it regards binomial distributions:
Where is the number of trials, is the number of 'successes,' is the probability of exactly successes in trials, and is the probability of a success occuring.
Statement 1 allows for a calculation of to be used in the probability calculation for the problem.
Statement 2 outright gives a to calculate the probability asked of in the problem.
Example Question #62 : Discrete Probability
The problem of an engine part performing succesfully is . A researcher performs a series of tests. Given trials, P is the probability of the part succeeding at least once. Is ?
1)
1)
Statement 2 alone is sufficient.
Either of the statements is sufficient.
Neither of the statements, separate or together, is sufficient.
Statement 1 alone is sufficient.
Together the two statements are sufficient.
Statement 1 alone is sufficient.
Since this probability question deals with successes and failures, it regards binomial distributions:
Where is the number of trials, is the number of 'successes,' is the probability of exactly successes in trials, and is the probability of a success occuring.
The probability of at least one success is the complement of exactly zero successes. Since we're looking at 3 trials, we can find the probability of zero successes to be and thus the complement, our .
For fewer than three trials, the probability will always be below , but for three or more, it depends on exactly how many trials there are, since the probability increases with increasing number of trials.
Example Question #116 : Arithmetic
students are being seated randomly in a row of chairs. What is the probability, that one of the students, Harold, will be seated in the chair second from the left?
1) There are students.
2) The probability of Maude, another student, sitting on the leftmost seat, while Dennis, another student, has the rightmost seat is .
Neither of the statements, separate or together, is sufficient.
Statement 2 alone is sufficient.
Together, the two statements are sufficient.
Statement 1 alone is sufficient.
Either of the statements is sufficient.
Either of the statements is sufficient.
Either of these statements can enable finding the probability of Harold sitting in a given seat, i.e. .
Statement 1 outright provides it, while Statement 2 can lead towards it with the relation
Example Question #121 : Arithmetic
A history class has recently finished their second test. A quarter of the class passed both tests. What percentage of those that passed the first test also passed the second?
1) A third of the class passed the first test.
2) Half of the class passed the second test.
Statement 1 alone is sufficient.
Statement 2 alone is sufficient.
Neither of the statements, separate or together, is sufficient.
Together, the two statements are sufficient.
Either of the statements is sufficient.
Statement 1 alone is sufficient.
This is a conditional probability problem, which follows the form:
In this case is the probability of passing the first test, is the probability of passing the second test, is then the probability of passing the second test, having passed the first, and is the probability of having passed both. The probability or percentage of students that passed the first test is necessary information.
Example Question #1101 : Data Sufficiency Questions
A card is removed from a standard deck of fifty-two cards, and one card is then chosen at random from the altered deck. Has the probability of the drawn card being red increased or decreased?
Statement 1: The removed card is a spade.
Statement 2: The card removed is a jack.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is 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.
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.
The probability of drawing a red card from a standard deck is .
If a red card is removed from a standard deck of fifty-two cards, and one card is chosen at random, the probability of it being red is . If a black card is removed, the probability is . Therefore, to answer the question, the color of the card must be known; the rank is irrelevant to the question. Statement 1 - but not Statement 2 - provides sufficient information.
Example Question #1106 : Data Sufficiency Questions
A card is removed from a standard deck of fifty-two cards and replaced by the joker, and one card is then chosen at random from the altered deck. Has the probability of the drawn card being black increased, decreased, or stayed the same?
Statement 1: The replaced card is not a heart.
Statement 2: The replaced card is not a club.
BOTH statements TOGETHER are insufficient 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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
The probability of drawing a black card from a standard, unaltered deck is .
If a red card is removed from a standard deck of fifty-two cards and replaced by the joker, and one card is chosen at random, all 26 black cards remain in a deck of 52, so the probability of the chosen card being black is still . If a black card is removed and replaced, there are 25 black cards out of 52 left, so the probability is . Therefore, to answer the question, the color of the card must be known. However, the two statements together, if assumed true, leave two possibilities open - the card could be a diamond (red) or a spade (black). The two statements together provide insufficient information.
Example Question #1107 : Data Sufficiency Questions
A card is removed from a standard deck of fifty-two cards and replaced by a card from another deck with the same backing. One card is then chosen at random from the first (altered) deck. Has the probability of the drawn card being black increased, decreased, or stayed the same?
Statement 1: The removed card and its replacement are both jacks.
Statement 2: The removed card and its replacement are of different suits.
BOTH statements TOGETHER are insufficient 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 sufficient to answer the question, but NEITHER statement ALONE is 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.
Assume both statements to be true. The probability of drawing a black card from a standard, unaltered deck is . We examine two cases.
Case 1: The jack of diamonds from the first deck was replaced by the jack of clubs from the other deck.
Then there are now 27 black cards in a deck of 52. The probability of drawing a black card at random from this deck has increased from to .
Case 2: The jack of clubs from the first deck was replaced by the jack of diamonds from the other deck.
Then there are now 25 black cards in a deck of 52. The probability of drawing a black card at random from this deck has decreased from to .
In both scenarios, the conditions of both statements were met; the removed card and its replacement were jacks of different suits. But in one scenario, the probability of drawing a black card increased, and in the other, it decreased. The two statements together provide insufficient information.