ISEE Lower Level Math : Outcomes

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

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Example Questions

Example Question #61 : Probability

A bag has \(\displaystyle 4\) red marbles, \(\displaystyle 5\) green marbles, and \(\displaystyle 6\) blue marbles. What is the probability of randomly drawing a red marble on the first draw?

Possible Answers:

\(\displaystyle \frac{1}{3}\)

\(\displaystyle \frac{1}{6}\)

\(\displaystyle \frac{4}{15}\)

\(\displaystyle \frac{2}{5}\)

Correct answer:

\(\displaystyle \frac{4}{15}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

For this question, we want a red marble. Since there are \(\displaystyle 4\) red marbles, we have \(\displaystyle 4\) wanted outcomes. Since there is a total of \(\displaystyle 15\) marbles, we have a total of \(\displaystyle 15\) possible outcomes.

The probability then becomes the following:

\(\displaystyle \text{Probability}=\frac{4}{15}\)

Example Question #62 : Probability

A bag has \(\displaystyle 4\) red marbles, \(\displaystyle 5\) green marbles, and \(\displaystyle 6\) blue marbles. What is the probability of randomly drawing a blue marble on the first draw?

Possible Answers:

\(\displaystyle \frac{4}{5}\)

\(\displaystyle \frac{1}{5}\)

\(\displaystyle \frac{3}{5}\)

\(\displaystyle \frac{2}{5}\)

Correct answer:

\(\displaystyle \frac{2}{5}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

For this question, we want a blue marble. Since there are \(\displaystyle 6\) blue marbles, we have \(\displaystyle 6\) wanted outcomes. Since there is a total of \(\displaystyle 15\) marbles, we have a total of \(\displaystyle 15\) possible outcomes.

The probability then becomes the following:

\(\displaystyle \text{Probability}=\frac{6}{15}=\frac{2\cdot 3}{5\cdot 3}=\frac{2}{5}\)

Example Question #63 : Probability

A bag has \(\displaystyle 4\) red marbles, \(\displaystyle 5\) green marbles, and \(\displaystyle 6\) blue marbles. What is the probability of randomly drawing a green marble on the first draw?

Possible Answers:

\(\displaystyle \frac{1}{3}\)

\(\displaystyle \frac{2}{3}\)

\(\displaystyle \frac{7}{15}\)

\(\displaystyle \frac{1}{5}\)

Correct answer:

\(\displaystyle \frac{1}{3}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

For this question, we want a green marble. Since there are \(\displaystyle 5\) green marbles, we have \(\displaystyle 5\) wanted outcomes. Since there is a total of \(\displaystyle 15\) marbles, we have a total of \(\displaystyle 15\) possible outcomes.

The probability then becomes the following:

\(\displaystyle \text{Probability}=\frac{5}{15}=\frac{5\cdot 1}{5\cdot 3}=\frac{1}{3}\)

Example Question #64 : Probability

A bag has \(\displaystyle 4\) red marbles, \(\displaystyle 5\) green marbles, and \(\displaystyle 6\) blue marbles. What is the probability of NOT drawing a blue marble on the first draw?

Possible Answers:

\(\displaystyle \frac{1}{15}\)

\(\displaystyle \frac{3}{5}\)

\(\displaystyle \frac{4}{5}\)

\(\displaystyle \frac{2}{3}\)

Correct answer:

\(\displaystyle \frac{3}{5}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

For this question, we do not want a blue marble. This means that we are trying to find the proability of drawing either a red or a green marble. Since we have \(\displaystyle 4\) red marbles and \(\displaystyle 5\) green marbles, we have \(\displaystyle 9\) wanted outcomes. Since there is a total of \(\displaystyle 15\) marbles, we have a total of \(\displaystyle 15\) possible outcomes.

The probability then becomes the following:

\(\displaystyle \text{Probability}=\frac{9}{15}=\frac{3\cdot 3}{3\cdot 5}=\frac{3}{5}\)

Example Question #65 : Probability

A bag has \(\displaystyle 4\) red marbles, \(\displaystyle 5\) green marbles, and \(\displaystyle 6\) blue marbles. What is the probability of NOT drawing a green marble on the first draw?

Possible Answers:

\(\displaystyle \frac{14}{15}\)

\(\displaystyle \frac{2}{3}\)

\(\displaystyle \frac{13}{15}\)

\(\displaystyle \frac{1}{3}\)

Correct answer:

\(\displaystyle \frac{2}{3}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

For this question, we do not want a green marble. This means that we are trying to find the proability of drawing either a blue or a green marble. Since we have \(\displaystyle 6\) blue marbles and \(\displaystyle 4\) red marbles, we have \(\displaystyle 10\) wanted outcomes. Since there is a total of \(\displaystyle 15\) marbles, we have a total of \(\displaystyle 15\) possible outcomes.

The probability then becomes the following:

\(\displaystyle \text{Probability}=\frac{10}{15}=\frac{2\cdot 5}{3\cdot 5}=\frac{2}{3}\)

Example Question #61 : Probability

If you randomly choose a number between \(\displaystyle 1\) and \(\displaystyle 10\), inclusive, what is the proability the chosen number is even?

Possible Answers:

\(\displaystyle \frac{1}{2}\)

\(\displaystyle \frac{1}{4}\)

\(\displaystyle \frac{1}{3}\)

\(\displaystyle \frac{1}{5}\)

Correct answer:

\(\displaystyle \frac{1}{2}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

First, write down the possible wanted outcomes:

\(\displaystyle 2, 4, 6, 8, 10\)

Now, because there are \(\displaystyle 5\) even numbers, we have \(\displaystyle 5\) wanted outcomes.

Since we are choosing numbers between \(\displaystyle 1\) and \(\displaystyle 10\), inclusive, we have a \(\displaystyle 10\) total outcomes.

The probability then can be written as the following:

\(\displaystyle \text{Probability}=\frac{5}{10}=\frac{5\cdot 1}{5\cdot 2}=\frac{1}{2}\)

Example Question #67 : Probability

If you randomly choose a number between \(\displaystyle 1\text{ and }10\), inclusive, what is the probability that the number is divisible by \(\displaystyle 4\)?

Possible Answers:

\(\displaystyle \frac{2}{5}\)

\(\displaystyle \frac{1}{5}\)

\(\displaystyle \frac{2}{9}\)

\(\displaystyle \frac{1}{6}\)

Correct answer:

\(\displaystyle \frac{1}{5}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

First, write down the possible wanted outcomes:

\(\displaystyle 4, 8\)

Now, because there are \(\displaystyle 2\) numbers divisible by four, we have \(\displaystyle 2\) wanted outcomes.

Since we are choosing numbers between \(\displaystyle 1\) and \(\displaystyle 10\), inclusive, we have a \(\displaystyle 10\) total outcomes.

The probability then can be written as the following:

\(\displaystyle \text{Probability}=\frac{2}{10}=\frac{2\cdot 1}{2\cdot 5}=\frac{1}{5}\)

Example Question #68 : Probability

If you randomly choose a number between \(\displaystyle 1\text{ and }10\), inclusive, what is the probability that the number is less than \(\displaystyle 9\), but greater than \(\displaystyle 3\)?

Possible Answers:

\(\displaystyle \frac{3}{5}\)

\(\displaystyle \frac{2}{5}\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle \frac{7}{10}\)

Correct answer:

\(\displaystyle \frac{1}{2}\)

Explanation:

Recall that a probability is the likelihood of something occurring.

Mathematically, we can write probability as the following:

\(\displaystyle \text{Probability}=\frac{\text{Number of wanted outcomes}}{\text{Total number of outcomes}}\)

First, write down the possible wanted outcomes:

\(\displaystyle 4, 5, 6, 7, 8\)

Now, because there are \(\displaystyle 5\) numbers that fit the criteria, we have \(\displaystyle 5\) wanted outcomes.

Since we are choosing numbers between \(\displaystyle 1\) and \(\displaystyle 10\), inclusive, we have a \(\displaystyle 10\) total outcomes.

The probability then can be written as the following:

\(\displaystyle \text{Probability}=\frac{5}{10}=\frac{5\cdot 1}{5\cdot 2}=\frac{1}{2}\)

Example Question #69 : Probability

If the probability of winning your next baseball game is \(\displaystyle p=0.73\), what is the probability that you do not win?

Possible Answers:

\(\displaystyle 0.01\)

\(\displaystyle 0.75\)

\(\displaystyle 0.27\)

\(\displaystyle 0.5\)

\(\displaystyle 0.8\)

Correct answer:

\(\displaystyle 0.27\)

Explanation:

The probability of an event not happening is one minus the probability it does happen.  

Since the probability of winning the game is \(\displaystyle 0.73\), then the probability of not winning would be,

 \(\displaystyle \\P_{lose}=1-P_{win} \\P_{lose}=1-0.73 \\P_{lose}=0.27\) .

Example Question #70 : Probability

If you have \(\displaystyle 5\) gold fish and \(\displaystyle 3\) beta fish, what is the probability you pick a beta fish if you randomly select one from you tank?

Possible Answers:

\(\displaystyle \frac{3}{8}\)

\(\displaystyle \frac{8}{3}\)

\(\displaystyle \frac{3}{5}\)

\(\displaystyle \frac{5}{3}\)

\(\displaystyle \frac{3}{10}\)

Correct answer:

\(\displaystyle \frac{3}{8}\)

Explanation:

To the probability of selecting a particular fish is the number of that fish divided by the total possible fish to choose from.  

The total is \(\displaystyle 5\) gold fish plus \(\displaystyle 3\) beta fish or \(\displaystyle 8\).  

So the probability of selecting a beta fish is 

\(\displaystyle P=\frac{beta}{all\ fish}=\frac{3}{5+3}=\frac{3}{8}\).

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