To find out how many students prefer tennis, one should add the number of the students who prefer basketball to the number of students who prefer volleyball.

The students who are not included among these  are the ones who prefer tennis. To find this number one should subtract  from the original group of students.

Therefore,  students prefer tennis. 

A multiple is a number that can be divided by another number (in this case 8) without a remainder. All of the answer choices can be divided by 8 without a remainder exept for the number 20 (which leaves a remainder of 4); therefore, 20 is not a multiple of 8.

Factors are numbers that can be multiplied together to create another number. 3, 4, 8, and 12 are all factors of 24.

There is no number that multiply by 7 to result in 24; therefore, 7 is not a factor of 24. 

If Bob and Brett planned a 5 day ski trip, then 2 days would make the trip 40 percent longer. 

This is because 2 extra days out of 5 is equal to . The percent equivalent of .4 is 40 percent. Therefore, 2 is the correct answer. 

If there are 15 cookies in a tin, and Rebecca gives 5 of the cookies to her mother, then 10 cookies remain. She gives one fifth of them, or 2 cookies, to her father.

Therefore, 8 cookies remain.

Rebecca has watched 6 and a half minutes of a video that is one hour and five minutes long, which can also be written as 6.5 minutes of a video that is 65 minutes long. 

Given that , Rebecca has watched 10% of the video. 

If there is a group of  green apples for every group of  red apples, then in every group of  apples there will be  green ones and  red ones. (). How many groups of  apples are there in a barrel containing  apples?  divided by  is , so there are  groups of  apples. In each group of  apples, there is a smaller group of  green apples, so there are  groups of  green apples each. , so there are  green apples in a barrel of  apples.

Alternatively, one could say that since there are  green apples in every group of  apples, the fraction of green apples in the barrel is . To find  of , multiply  and  together.  is , so there are  green apples in the barrel.

There are five segments of line between points A and F.  divided by  is , so each line segment is  inches long. There are  line segments between points A and C.  line segments  inches each  inches, so  inches is the correct answer.

Alternatively, since there are  line segments between points A and F and  line segments between points A and C, line AC is  of the total line AF. To find  of , multiply  and .  , so the correct answer is  inches.

There is a shipment of computer screens arriving today. If there are 1,400 screens, and 35% of them are 23 inches wide, what is the number of 23 inch-wide screens?

We need to find the portion of screens from the whole. 

First, we need to convert our percent to a decimal:

Next, multiply the total number by our new-found decimal

So our answer is 490