What is the surface area of a circular clarifier 55 feet in diameter? - ProProfs Discuss

# What is the surface area of a circular clarifier 55 feet in diameter?

A. 1,256 square feet
B. 1,520 square feet
C. 1,963 square feet
D. 2,375 square feet
E. 2,826 square feet

This question is part of CA Water Treatment Plant Operator Quiz Chapter 3
Asked by PaulMJr, Last updated: Feb 22, 2020

#### Danny R. Glover

Danny R. Glover, Editor, New York City

The correct answer to this item is letter D. To get the surface area of a circle, one must use the formula r squared multiply by pi. Since the radius is not given, divide the diameter by 2. So, 55 ft divided by 2 is 27.5 and this will be the radius.

Next, multiply 27.5 by 27.5 and the product will be 756.25. The value of pi is 3.14 where we multiply 756.25 to it. We will get the answer of 2,374.625. Usually, the answer is rounded off to retain a whole number; the final answer will be 2,375 square feet. Whether the radius or the diameter is given and memorize the value of pi, you can easily solve for the surface area of circles.

#### RagweedFarmer

RagweedFarmer

2,375.835 sq ft
math constant: area of a circle formula, diameter squared x 0.7854 (0.7854 is 1/4th of pi, 3.1416/4=0.7854)
55x55x0.7854=2,375.835 sq ft

John Smith