Please help out. Max points given a=12; b=?; c=22

Study the Problem

What is the cost of the wallpaper (in dollars per square foot)?

Organize the Facts

The wallpaper covers a rectangle 42 ft by 25.5 ft. It costs $771.12 for that area.

Make a Plan

To find dollars per square foot, we need to divide the dollar amount by the area in square feet. The area needs to be computed. It is the area of a rectangle, so can be found by multiplying length and width.

Plan: multiply length and width of the wall to find its area; divide the cost by that area to find dollars per square foot.

Execute the Plan

area = (42 ft)×(25.5 ft) = 1071 ft²

cost/area = $771.12/(1071 ft²) = $0.72/ft²

Examine the Results

The area is on the order of 40×25 = 1000 ft², and the cost is less than $1000, so the cost will be less than $1 per square foot. The answer is in the right ballpark. If we multiply it out, we should get the given cost:

... 0.72×42×25.5 = 771.12 . . . . agrees with given cost.

The cost of the wallpaper is $0.72 per square foot.

You would have a cylinder if you put two refraction cups together.