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Question

The perimeter of an equilateral triangle is $36\sqrt{3}$ m. Find the height (in metres).

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper PDF (31-Jan-2021) (Shift 1)
The correct answer is
18

Equilateral Triangle Properties

An equilateral triangle has three equal sides and three equal angles (each 60 degrees). The perimeter is the total length of all sides.

Calculating Side Length from Perimeter

Given the perimeter ($P$) of the equilateral triangle is $36\sqrt{3}$ m.

The formula for the perimeter is $P = 3 \times side$. Let the side length be '$s$'.

So, $3s = 36\sqrt{3}$ m.

To find the side length, divide the perimeter by 3:

$s = \frac{36\sqrt{3}}{3} = 12\sqrt{3} \text{ m}$

Finding the Height

The formula for the height ($h$) of an equilateral triangle with side length '$s$' is:

$h = \frac{\sqrt{3}}{2} \times s$

Substitute the calculated side length ($s = 12\sqrt{3}$ m) into the height formula:

$h = \frac{\sqrt{3}}{2} \times (12\sqrt{3})$

Multiply the terms:

$h = \frac{12 \times (\sqrt{3} \times \sqrt{3})}{2}$

Since $\sqrt{3} \times \sqrt{3} = 3$:

$h = \frac{12 \times 3}{2} = \frac{36}{2}$

$h = 18 \text{ m}$

Therefore, the height of the equilateral triangle is 18 metres.

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