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.