Question

find the area of an equilateral triangle whose perimeter is 18 cm​

Answer 1

Answer:

if it is an equilateral triangle so each side will be 6 cm

area = 1/2bh

= 1/2 × 6 × 5.1

so the area is 15.3 cm

Explanation:

the height is y

if we cut the triangle into half

the base will be 3 cm and one side will be 6cm so the height will be calculated by Pythagoras theorem

9 + X2 = 36

X2=27

x = 5.1

Answer 2

Answer:

$\huge\fbox\red{\fbox\green{Done \: by \: Aritra \: Kar}}$

Explanation:

$Given: \: - \\ Perimeter = 18 \: cm \\ so ,\: side(a) \: = \frac{18}{3} = 6 \: cm \\ Area \: of \: a \: equilateral \: triangle= \frac{ \sqrt{3} \times {a}^{2} }{4} \\ = > \frac{ \sqrt{3} \times {6}^{2} }{4} \\ = > \frac{ \sqrt{3} \times 36}{4} = > \sqrt{3} \times 9 \\ = > 9 \sqrt{3} (ans)$