ISEE Middle Level Math : How to find the probability of an outcome

Study concepts, example questions & explanations for ISEE Middle Level Math

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Example Questions

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Example Question #1 : Probability

There are 32 marbles in a bag: 7 are Red, 11 are Blue, 8 are Purple and 6 are Green. If I pick one marble out of the bag, which color would it most likely be?

Possible Answers:

Correct answer:

Explanation:

Find the color with the largest number of marbles in the bag.

Answer: There are more blue marbles in the bag, therefore it would be more likely to pick a blue marble.

Example Question #2 : Probability

The red queens are removed from a standard deck of fifty-two cards. What is the probability that a card randomly drawn from that modified deck will be a face card (jack, queen, king)?

Possible Answers:

Correct answer:

Explanation:

There are four cards of each rank in a standard deck; since three ranks - jacks, queens, kings - are considered face cards, this makes twelve face cards out of the fifty-two. But two of those face cards - two red queens - have been removed, so now there are ten face cards out of fifty. This makes the probability of a randomly drawn card being a face card

.

Example Question #2 : Probability

Jamie rolled a normal 6-sided die. What is the probability of rolling a number greater than 4?

Possible Answers:

Correct answer:

Explanation:

Probability is determined by dividing the number of incidences of a specific outcome (in this case rolling greater than 4, or rolling a 5 or 6) by the total number of outcomes (there are 6 sides to the die).

Example Question #3 : Probability

What is the probability of drawing a diamond from a regular set of playing cards?

Possible Answers:

Correct answer:

Explanation:

Probability is determined by dividing the number of outcomes of a particular event by the total number of events. In a regular deck of playing cards, there are 52 cards and 13 diamonds.

Example Question #4 : Probability

What is the probability of drawing a red jack from a standard deck of playing cards?

Possible Answers:

Correct answer:

Explanation:

A standard deck contains  cards including jacks, of which are red. Therefore, the probability is:

Example Question #5 : Probability

There are 5 yellow pebbles, 12 orange pebbles, and 8 red pebbles.  What is the probability of picking a red or yellow pebble?

Possible Answers:

Correct answer:

Explanation:

There are 13 yellow and red pebbles.  There are 25 pebbles total.  Therefor the probability of choosing a red or yellow pebble is .

Example Question #6 : Probability

There are 6 red marbles, 4 purple marbles, and 9 green marbles in a bag.  What is the probablility of randomly drawing a green marble?

Possible Answers:

Correct answer:

Explanation:

First we need to determine the total number of marbles in the bag:

\dpi{100} 6+4+9=19\ marbles

There are 9 green marbles, so the probability of drawing one of those 9 marbles out of 19 possible marbles is \dpi{100} \frac{9}{19}.

Example Question #7 : Probability

A bag contains red marbles, pink marbles, and purple marbles. What is the probability of not choosing a purple marble?

Possible Answers:

Correct answer:

Explanation:

The probability (p) is equal to the number of a specific event (purple marbles) divided by the total number of events. The probability of NOT p (called q) is equal to In this example:

Example Question #1 : How To Find The Probability Of An Outcome

A bag of marbles contains 8 black marbles, 4 red marbles, 3 blue marbles, and 5 white marbles. What is the probability of not drawing a black marble?

Possible Answers:

Correct answer:

Explanation:

Probability is determined by dividing the possible number of instances of a particular outcome by the total number of possible outcomes. Therefore, we need to find the probability of drawing red, blue, or white divided by the total number of outcomes.

Example Question #9 : Probability

If you meet a random person on the street, what is the probability he or she was born on a weekend?

Possible Answers:

Correct answer:

Explanation:

There are seven days in a week.

The probability that a person you meet was born on any particular day is .

The question asks for the probability that the person you meet was born on a weekend (Saturday or Sunday). Therefore, we must add the probability of being born on either day:

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