To find the area of an ellipse, we use the formula:
Area = π × a × b
Where:
-
a is half of the horizontal width (semi-major or semi-minor axis)
-
b is half of the vertical height (the other semi-axis)
-
π is approximately 3.1416 (we’ll use 3.14 for simplicity unless told otherwise)
But note: In each diagram, the numbers given are the
full widths and heights, not the halves. So we must divide each by 2 to get
a and
b.
Let’s solve each one step by step.
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Problem 1:
Horizontal = 10 → a = 10 ÷ 2 = 5
Vertical = 5 → b = 5 ÷ 2 = 2.5
Area = π × 5 × 2.5 = 3.14 × 12.5 =
39.25
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Problem 2:
Horizontal = 8 → a = 4
Vertical = 4 → b = 2
Area = π × 4 × 2 = 3.14 × 8 =
25.12
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Problem 3:
Horizontal = 2 → a = 1
Vertical = 3 → b = 1.5
Area = π × 1 × 1.5 = 3.14 × 1.5 =
4.71
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Problem 4:
Horizontal = 15 → a = 7.5
Vertical = 5 → b = 2.5
Area = π × 7.5 × 2.5 = 3.14 ×
Parent Tip: Review the logic above to help your child master the concept of circles and ellipses worksheet.
