# Common Core: 7th Grade Math : Develop a Uniform Probability Model by Assigning Equal Probability to all Outcomes: CCSS.Math.Content.7.SP.C.7a

## Example Questions

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### Example Question #11 : Probability

Gina has a bag of 12 marbles. The bag is half black marbles and half white marbles. If Gina picks out two random marbles, and both are white, what is the percent chance that the next marble she picks will also be white?

20 percent

60 percent

40 percent

50 percent

40 percent

Explanation:

Given that in Gina’s bag of 12 marbles, half of them are black and half are white, this means that there are 6 black marbles and 6 white marbles. However, because she already picked out 2 white marbles, this means that there are now only 4 out of 10 white marbles left. 4 out of 10 converts to 40 percent, which is therefore the correct answer.

### Example Question #1 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

At Lisa's school,  of her class consists of girls. There are  students in her class. On the first day of school,  girls wore skirts. How many girls did not wear skirts?

Explanation:

Given that  of the class is girls, and there are  students, we must first determine how many girls are in the class.

Because  is double the value of ,  is double the value of should be half of .

If  of the  girls wear skirts, then we can subtract to find the number of girls not wearing skirts.

### Example Question #21 : Probability

Billy's mom baked a pizza with eight slices. Half the slices have pepperoni only. Two of the slices have both pepperoni and onions. One slice has onions only. One slice has only cheese.

If Billy is allergic to pepperoni, and takes a slice of pizza with his eyes blindfolded, what is the percentage chance that he will select a piece he is not allergic to?

Explanation:

The pizza that Billy's mom baked was composed of these types of slices:

Half the slices have pepperoni only. Two of the slices have both pepperoni and onoins. One slice has onions only. One slice has only cheese.

Therefore,

Billy could eat either the onion only slice, or the cheese only slice. This means that out of  pieces of pizza, he could eat

Given that  is the percent equivalent of , that is the correct answer.

### Example Question #4 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Megan has a bag of marbles containing  pink marbles,  orange marbles,  green marbles, and  yellow marbles. What is the probability that Megan will pick a pink marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Megan wants to know what her probability is of drawing a pink marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there are  pink marbles; therefore,

### Example Question #5 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Megan has a bag of marbles containing  pink marbles,  orange marbles,  green marbles, and  yellow marbles. What is the probability that Megan will pick an orange marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Megan wants to know what her probability is of drawing an orange marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there are  orange marbles; therefore,

### Example Question #6 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Megan has a bag of marbles containing  pink marbles,  orange marbles,  green marbles, and  yellow marbles. What is the probability that Megan will pick a green marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Megan wants to know what her probability is of drawing a green marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there are  green marbles; therefore,

### Example Question #2 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Megan has a bag of marbles containing  pink marbles,  orange marbles,  green marbles, and  yellow marbles. What is the probability that Megan will pick a yellow marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Megan wants to know what her probability is of drawing a yellow marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there are  yellow marbles; therefore,

### Example Question #8 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Samantha has a bag of marbles containing  pink marbles,  orange marble,  red marbles,  purple marbles,  white marbles,  black marble,  green marbles, and  yellow marble. What is the probability that Samantha will pick a orange marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Samantha wants to know what her probability is of drawing a orange marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there is  orange marble; therefore,

### Example Question #9 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Samantha has a bag of marbles containing  pink marbles,  orange marble,  red marbles,  purple marbles,  white marbles,  black marble,  green marbles, and  yellow marble. What is the probability that Samantha will pick a pink marble out of the bag?

Explanation:

In this problem we have a total of  marbles. That means that each marble, regardless of color, has a  chance of being picked, as shown in the images below. This image shows equal probability because each marble has a  chance of being drawn, which is equal to the probability of all of the other marbles.

Samantha wants to know what her probability is of drawing a pink marble out of her bag. Remember, probability is the number of favorable outcomes over the total number of outcomes:

For this problem there are  pink marbles; therefore,

### Example Question #10 : Develop A Uniform Probability Model By Assigning Equal Probability To All Outcomes: Ccss.Math.Content.7.Sp.C.7a

Samantha has a bag of marbles containing  pink marbles,  orange marble,  red marbles,  purple marbles,  white marbles,  black marble,  green marbles, and  yellow marble. What is the probability that Samantha will pick a white marble out of the bag?