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

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

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Example Questions

Example Question #51 : How To Find The Probability Of An Outcome

If Rebecca rolls a pair of dice, what is the probability that the sum an even number?

Possible Answers:

Correct answer:

Explanation:

If Rebecca rolls a pair of dice, the potential numbers that she could roll are below:

Thus, there are 11 possible numbers that she could roll, of which 6 are even. 

Therefore, the probability of rolling an even number is .

Example Question #52 : How To Find The Probability Of An Outcome

If Alicia makes 1 out of 7 of the soccer goals that she attempts, how many goals will she score if she attempts 49 goals (assuming that her accuracy rate remains the same)?

Possible Answers:

Correct answer:

Explanation:

If Alicia makes 1 out of 7 of the soccer goals that she attempts, this means that she makes  of her attempted soccer goals. 

If Alicia makes 49 soccer goal attempts, she will score on  of them. Given that  of 49 is 7, the correct answer is 7.

Example Question #53 : How To Find The Probability Of An Outcome

If Mary rolls a pair of dice, what is the probability that the the sum will be a multiple of 4?

Possible Answers:

Correct answer:

Explanation:

When a pair of dice is rolled, there are 11 possibilities. 

The multiples of 4 are 4, 8, and 12. 

Therefore, the probability of rolling a multiple of 4 is .

Example Question #54 : Data Analysis And Probability

If 1 in 5 corgis will develop back problems, what are the odds that Virgo, a 6 month old corgi, will develop back problems?

Possible Answers:

20 percent

10 percent

50 percent

40 percent

Correct answer:

20 percent

Explanation:

Given that Virgo is a corgi, and that 1 in 5 corgis develop back problems, there is a 20 percent chance that Virgo will develop back problems. This is because 1 divided by 5 is .2, which is equivalent to 20 percent. 

Example Question #54 : How To Find The Probability Of An Outcome

In a cupboard there are  mugs,  glasses and  plastic cups. If someone randomly reaches into the cupboard and grabs one of these items, what is the probability that he or she will pull out a mug?

Possible Answers:

Correct answer:

Explanation:

To write probability as a fraction, put the number of things that match what you're looking for in the numerator and the total number of things in the denominator. In this case, what we're looking for is mugs. There are  mugs, so we'll put  in the numerator. The total number of things in the cupboard is  mugs  glasses  cups. , so we'll put  in the denominator. This gives us , which we can simplify to . The correct answer is .

Example Question #55 : Data Analysis And Probability

What is the probabily of getting  or  when you roll a die?

Possible Answers:

Correct answer:

Explanation:

There are  equally likely outcomes when rolling a die so each one of them has a probability of .  When you are finding the probability of a intersection, one event or another happening, you add the probabilities together.  So the probability of rolling a  plus the probability of rolling a  equals .

Example Question #55 : How To Find The Probability Of An Outcome

A bag has  red marbles,  green marbles, and  blue marbles. What is the probability of NOT drawing a red marble on the first draw?

Possible Answers:

Correct answer:

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

For this question, we do not want a red marble. This means that we are trying to find the proability of drawing either a blue or a green marble. Since we have  blue marbles and  green marbles, we have  wanted outcomes. Since there is a total of  marbles, we have a total of  possible outcomes.

The probability then becomes the following:

Example Question #56 : How To Find The Probability Of An Outcome

If you randomly choose a number between , inclusive, what's the proability the number will be divisible by ?

Possible Answers:

Correct answer:

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

First, write down the possible wanted outcomes:

Now, because there are  numbers divisible by three, we have  wanted outcomes.

Since we are choosing numbers between  and , inclusive, we have a  total outcomes.

The probability then can be written as the following:

Example Question #57 : Data Analysis And Probability

If you randomly choose a number between , inclusive, what is the probability that the number is less than ?

Possible Answers:

Correct answer:

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

First, write down the possible wanted outcomes:

Now, because there are  numbers that are less than , we have  wanted outcomes.

Since we are choosing numbers between  and , inclusive, we have a  total outcomes.

The probability then can be written as the following:

Example Question #54 : Outcomes

If you randomly choose a number between , inclusive, what is the probability that the number is negative?

Possible Answers:

Correct answer:

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

First, write down the possible wanted outcomes. However, since all the numbers we are choosing from are negative, we have  wanted outcomes.

Since we are choosing numbers between  and , inclusive, we have a  total outcomes.

The probability then can be written as the following:

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