You make and sell triangular flags. Each flag has a base of 3.5 feet and a height of 2.5 feet. Fabric for the flags costs $0.40 per square foot. What is the cost to make one flag?

(Base * Height) / 2 = Area of triangle (in unit squared) - putting this equation to this we get:

(3.5 * 2.5) / 2 = square feet

8.75/2 = 4.375 square feet

So the area to make one triangular flag is 4.375 square feet. So the cost to make one flag is:

4.375 * cost per square foot = cost per flag

4.375 * 0.40 = $1.75

The answer is $1.75.

Note: Apologies if I didn't spell square foot or feet right - I am from New Zealand and we work in meters.