Final answer:
The cross-sectional area of a steel pipe with a 20-inch outside diameter is approximately 2.1812 square feet, calculated using the formula for the area of a circle, A = πr².
Step-by-step explanation:
To find the cross-sectional area of a steel pipe with an outside diameter of 20 inches, we need first to convert the diameter from inches to feet, considering that 1 inch equals 0.08333 feet. So, the diameter in feet is 20 inches × 0.08333 feet/inch = 1.6666 feet. The radius is half of the diameter, which is 1.6666 feet / 2 = 0.8333 feet. The formula for the cross-sectional area of a circle is A = πr², where A is the area and r is the radius of the circle.
Substituting the radius into the formula gives us:
A = π × (0.8333 feet)²
A = 3.14159 × (0.8333 feet) × (0.8333 feet)
A = 3.14159 × 0.69444 square feet
A = 2.1812 square feet (approximately).
The cross-sectional area of the steel pipe is therefore roughly 2.1812 square feet.