If there are 250 emitters per acre and each wets a circular area of radius 15 inches, what fraction of an acre is wetted per acre?

• A. 0.028 acres
• B. 0.050 acres
• C. 0.100 acres
• D. 0.010 acres

Answer: (A)

The idea is to find how much area all the emitters cover together and express that as a fraction of one acre. Each emitter wets a circle with radius 15 inches, which is 1.25 feet. The area of one circle is pi r^2 = pi × (1.25)^2 ≈ 4.9087 square feet.

With 250 emitters, the total wetted area is 250 × 4.9087 ≈ 1,227 square feet. Since one acre is 43,560 square feet, the fraction wetted per acre is 1,227 / 43,560 ≈ 0.0282 acres. So about 0.028 acres, i.e., roughly 2.8% of an acre, is wetted. This assumes the wetted circles don’t overlap; overlaps would reduce the actual fraction in practice, but the straightforward calculation uses the sum of individual areas.