Which of the following statements contain a variable? check all that apply.

a. the number of different colors on the page.
b. they scored 27 points.
c. eighty miles per hour.
d. half the speed of the car.

The correct answers are:

A) the number of different colors on the page; and 
D) half the speed of the car.

Explanation:

A variable represents an unknown amount.  

For A, we do not know how many colors are on the page; this means we would use a variable to represent it.

For D, while we know we want half of the speed of the car, we do not know what the speed of the car actually is; therefore we would use a variable to represent it.