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

Given that, area = 10 sq cm,
perpendicular = 20 cm and base = ?
area = (base x perpendicular) / 2

Correct Option: A

Given that, area = 10 sq cm,
perpendicular = 20 cm and base = ?
area = (base x Perpendicular) / 2
⇒ 10 = (base x 20) / 2
∴ base = 1 cm

Given that,
area = 40 sq cm,
base = 28 cm and
height = perpendicular = ?

Area = (base x perpendicular) / 2

Correct Option: C

Given that,
area = 40 sq cm,
base = 28 cm and
height = perpendicular = ?

Area = (base x perpendicular) / 2
⇒ 40 = (28 x perpendicular) / 2
∴ perpendicular = 40/14 = 20/7
= 2⁶/₇ cm

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

Area of parallelogram = Base x Height
= 8.06 x 2.08

Correct Option: C

Area of parallelogram = Base x Height
= 8.06 x 2.08 = 16.76 cm²