Given that, a = 6 cm, b = 4 cm and c = 5 cm
Required perimeter = a + b + c

Correct Option: D

Given that, a = 6 cm, b = 4 cm and c = 5 cm
Required perimeter = a + b + c
= 6 + 4 + 5 cm
= 15 cm

Given that, a = 8 cm, b = 10 cm and c = 12 cm

We know, that
s = (a + b + c)/2

Area = √s(s - a) (s - b) (s - c)

Correct Option: B

Given that, a = 8 cm, b = 10 cm and c = 12 cm

We know, that
s = (a + b + c)/2
= (8 + 10 + 12)/2
= 30/2 = 15 cm

∴ (s - a) = (15 - 8) = 7 cm
(s - b) = (15 - 10) = 5 cm
(s - c) = (15 - 12) = 3 cm

∴ Area = √s(s - a) (s - b) (s - c)
= √15 x 7 x 5 x 3
= √1575
= √25 x 63
= 5√63 cm

Req. Area = √3/4 x a²

Correct Option: B

Req. Area = √3/4 x a² = √3/4 x 8² cm²
= 16√3 cm²

Area of equilateral triangle = √3/4 a² = 4√3.

Correct Option: D

Area of equilateral triangle = √3/4 a² = 4√3.
⇒ a² = 16
∴ a = 4 cm

Area = 1/2 hectare = 10000 / 2 m²
= 5000 m²

Again Area = 1/2 x (Diagonal)²

Correct Option: B

Area = 1/2 hectare = 10000 / 2 m²
= 5000 m²

Again Area = 1/2 x (Diagonal)²

So 1/2 x (Diagonal)² = 5000m²
⇒ Diagonal²= 10000
∴ Diagonal = 100