A sailing course is in the shape of an equilateral triangle. If the course has an altitude of 9 mi, what is the perimeter of the triangle?

27mi

Step-by-step explanation:

Since the sailing course is equilateral in shape, then all their sides are equal.

Get one of the sides using Pythagoras theorem as shown;

Let one of the side be x

Two base will be x/2

According to the theorem;

x² = 9² +(x/2)²

x² = 81 + x²/4

x²-x²/4 = 81

3x²/4 = 81

3x² = 324

x² = 324/4

x² = 81

x = 9

Perimeter of the triangle = 3x

Perimeter of the triangle = 3(9)

Perimeter of the triangle = 27mi

the answer is 15% decrease

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