The base of a right pyramid is a square of side 10 cm. If its height is 10 cm, then the area ( in cm2) of its lateral surface is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 1 i.e. 100√5
Concept
Lateral surface = (1/2) × Perimeter of the base × Slant height
Application
Join EF which is the slant height of this figure.
EO = height = 10 cm
In right triangle EOF
By pythagorous theorem
EF2 = OE2 + OF2
102 + 52
Slant height = EF = √125 = 5√5
Perimeter of base = 4 x 10 = 40cm
Lateral Surface Area = (1/2) × Perimeter of the base × Slant height
(1/2) x 40 x 5√5 = 100√5