Area and Surface Area
Calculate area of 2D shapes and surface area of 3D shapes.
Learn
Key Formulas
- Rectangle: A = length x width
- Triangle: A = (1/2) x base x height
- Circle: A = pi x r^2
- Rectangular prism surface area: SA = 2lw + 2lh + 2wh
Practice
Question 1: Find the area of a rectangle with length 8 cm and width 5 cm.
Answer
A = 8 x 5 = 40 cm^2
Question 2: Find the area of a triangle with base 12 m and height 7 m.
Answer
A = (1/2)(12)(7) = 42 m^2
Question 3: Find the area of a circle with radius 5 in. (Use pi = 3.14)
Answer
A = 3.14 x 25 = 78.5 in^2
Question 4: A rectangular box has dimensions 4 x 3 x 2. Find surface area.
Answer
SA = 2(4x3) + 2(4x2) + 2(3x2) = 24 + 16 + 12 = 52 square units
Question 5: A square has perimeter 20 cm. Find its area.
Answer
Side = 20/4 = 5 cm. Area = 5 x 5 = 25 cm^2
Question 6: Find the area of a parallelogram with base 9 ft and height 6 ft.
Answer
A = base x height = 9 x 6 = 54 ft^2
Question 7: A cube has edges of 4 cm. Find surface area.
Answer
SA = 6 x (4^2) = 6 x 16 = 96 cm^2
Question 8: The area of a rectangle is 48 m^2. If width is 6 m, find length.
Answer
48 = L x 6, so L = 8 m
Question 9: A trapezoid has bases 5 and 9, height 4. Find area.
Answer
A = (1/2)(b1 + b2)h = (1/2)(14)(4) = 28 square units
Question 10: A circle has diameter 10 cm. Find area. (Use pi = 3.14)
Answer
r = 5, A = 3.14 x 25 = 78.5 cm^2