Question

1. Savita has a lamp placed at the centre of her square yard, each side measuring 20 m. The light of lamp covers a circle of radius 10 m on yard. What area of the yard is NOT lit by the tamp?
A. 400 sq.m
B. 100m sq. m
C. (40-10m) sq. m
D. (400-100m) sq. m​

Answer 1

Given :- Each side measuring 20 m. The light of lamp covers a circle of radius 10 m on yard.

To Find :- What area of the yard is NOT lit by the

lamp ?

A. 400π sq. m

B. 100π sq. m

C. (40 - 10π) sq. m

D. (400 - 100π) sq. m

Formula used :-

• Area of square = (Side)²
• Area of circle = π(radius)²

Solution :-

As given that,

→ Each side of square yard = 20 m

So,

→ Area of square yard = (20)² = 400 m² --------- Equation (1)

now,

→ Radius of circle covered by lamp = 10 m

So,

→ Area of circle covered by lamp = π(10)² = π × 100 = 100π m² ------------ Equation (2)

then,

→ Area of yard not lit by the lamp = Area of square yard - Radius of circle covered by lamp

→ Area of yard not lit by the lamp = Equation (1) - Equation (2)

→ Area of yard not lit by the lamp = (400 - 100π) m² (D) (Ans.)

therefore, the area of the yard is not lit by the

lamp is equal to (400 - 100π) sq. m .

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