The area of a semicircle of radius 4r is
(a) 8πr²
(b) 4πr²
(c) 12πr²
(d) 2πr²

Solution:

Given, radius of semicircle is 4r

We have to find the area of the semicircle

Area of semicircle = πr²/2

Where, r is the radius of the circle

Given, r = 4r

Area = π(4r)²/2

= 16πr²/2

= 8πr²

Therefore, the area of the semicircle is 8πr² square units.

✦ Try This: The area of a semicircle of radius 2r is

Given, radius of semicircle is 2r

We have to find the area of the semicircle

Area of semicircle = πr²/2

Where, r is the radius of the circle

Given, r = 2r

Area = π(2r)²/2

= 4πr²/2

= 2πr²

Therefore, the area of the semicircle is 2πr² square units.

☛ Also Check: NCERT Solutions for Class 7 Maths Chapter 11

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NCERT Exemplar Class 7 Maths Chapter 9 Problem 37

The area of a semicircle of radius 4r is (a) 8πr², (b) 4πr², (c) 12πr², (d) 2πr²

Summary:

The area of a semicircle of radius 4r is 8πr² square units.

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