The perimeter of an equilateral triangle ABC is 10.2 cm. What is the area of the triangle ?

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  1. \(18.9\sqrt{3} \, \text{cm}^2 \)
  2. \(1.89\sqrt{3} \, \text{cm}^2\)
  3. \(2.89\sqrt{3} \, \text{cm}^2 \)
  4. \(28.9\sqrt{3} \, \text{cm}^2 \)

Answer (Detailed Solution Below)

Option 3 : \(2.89\sqrt{3} \, \text{cm}^2 \)
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Detailed Solution

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Given:

The perimeter of an equilateral triangle ABC is 10.2 cm.

Formula used:

Area of an equilateral triangle = \( \dfrac{\sqrt{3}}{4} \times a^2\)

Where, a = side length of the equilateral triangle

Calculation:

The perimeter of an equilateral triangle = 3a

⇒ 3a = 10.2

⇒ a = 3.4 cm

Area = \(\dfrac{\sqrt{3}}{4} \times (3.4)^2\)

⇒ Area = \(\dfrac{\sqrt{3}}{4} \times 11.56\)

⇒ Area = \(2.89\sqrt{3}\) cm2

∴ The correct answer is option 3.

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