The cost of painting a circular traffic sign is $3.50 per square foot. How much, to the nearest dollar, will it cost to paint the sign if its diameter measures 36 in?

A = pi (r^2)

1. Calculate radius:

r = d/2, so r = 18

2. Enter variable into equation

a = pi (r^2)

becomes a = 3.14 (18^2)

3. Solve

a = 3.14 (324)

a ~ = 1018 in2

4. Convert to feet

1018/12 = 84 ft2

5. Multiply by unit rate

84 (3.5) = $294

It will cost $294 to paint the sign.