Question

Construct a Equilateral triangle ABC. whose perimeter is 21cm

Answer 1

Construction of an equilateral triangle :

Here, the equilateral triangle is of 21cm. So, our construction will be of 7cm as each side.

Step 1 :

• Draw a line AB of 7cm.

Step 2 :

• Cut an arc of 7cm from point A.

Step 3 :

• Keeping the needle of the compass at point B cut an arc of 7cm which will intersect the previous arc.

Step 4 :

• Join the points and thus formed an equilateral triangle.

Hence, we are done.

Answer 2

Required Answer :

To construct this equilateral triangle first we should know value of side of triangle.

Given:

• perimeter of triangle = 21 cm

Let

• side of triangle = x

we know :

$\checkmark\boxed{\text{perimeter of triangle} = \rm{}side_1 + side_2+side_3}$

$\hookrightarrow \sf{}21 = \sf{}x \times x \times x$

$\hookrightarrow \sf{}21 =3x$

$\hookrightarrow \sf{}3x = 21$

$\hookrightarrow \sf{}x = \dfrac{21}{3}$

$\hookrightarrow \sf{}x = \dfrac{7 \times 3}{3}$

$\hookrightarrow \sf{}x = \dfrac{7 \times\cancel 3}{\cancel3}$

$\hookrightarrow \sf{}x = 7 \times 1$

$\hookrightarrow \boxed{\sf{}x = 7 } \star$

$\therefore \: \: \underline{ \sf{}side \: of \: equilateral \: triangle = \textbf{7 \: cm}}$

For construction of triangle see attached picture ✔

steps to contruct the equilateral triangle:

• Contruct a line AB of length 7cm

• Now take a compus and keep it on point A

• Make an ark with distance of 7cm from point A

• Do same with point B

• The point where both arks meet name it as C

• Join C with A and B