Question

What is the surface area of the regular pyramid given below ?

Answer 1

Choice C is correct answer.

Explanation:

We have to find the surface area of of regular pyramid.

From given diagram , we observe that

Base = 9 units height = 7 units

The formula for total surface area of pyramid is

T.S.A = L.S.A + B

Total surface area of regular pyramid is sum of Lateral surface area and area of base.

L.S.A = 1/2pl where p is perimeter and l is height.

B = s² is area of base where s is base.

Hence, T.S.A = 1/2pl+ s²

Firstly, we have to find the perimeter.

p = 4s

p = 4(9) = 36 units

T.S.A = 1/2(36)(7)+(9)²

T.S.A = (18)(7) + 81

T.S.A = 126+81

T.S.A = 207 units.

Hence, the surface area of regular pyramid of 207 units.

Answer 2

Option C
`207\ units^(2)`

Explanation:

we know that

the surface area of a pyramid is equal to

`SA=B+LA`

where

B is the area of the base

LA is the lateral area

The area of the base B is

`B=9*9=81\ units^(2)`

The lateral area is equal to

`LA=4*(1/2)(9*7)=126\ units^(2)`

the surface area is equal to

`SA=81+126=207\ units^(2)`