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Surface Area
Definition Of Surface Area
The surface area of a three-dimensional figure is the sum of the areas of all its faces.
Example of Surface Area
The formula for the total surface area of a cone is πr2 + πrl.
= π × 102 + π × 10 × 39
= 100π + 390π
= 490π
Video Examples: Surface Area
Solved Example on Surface Area
Ques: An oil tank is 42 ft tall with a diameter of 88 ft. What is its surface area? Take π = 3.
Choices:
A. 22,704 square feet
B. 22,703 square feet
C. 23,763 square feet
D. 22,705 square feet
Correct Answer: A
Solution:
Step 1: The oil tank is in the shape of a cylinder.
Step 2: The cylinder has two circles and one rectangle.
Step 3: So, the surface area of the oil tank = 2 × area of the circle + area of the rectangle.
Step 4: Surface area = 2πr2 + bh
Step 5: = 2 × 3 × 44 × 44 + 2 × 3 × 44 × 42
Step 6: = 11,616 + 11,088 = 22,704 square feet
Step 7: The surface area of the oil tank = 22,704 square feet.