Question

find the circumference of a circle whose area is 4 times the area of a circle with diameter 21 CM

Answer 1

Answer:

Diameter = 21 cm

So, radius = 21/2 cm

= 10.5 cm

So, area of the circle = pi x r square

= 22/7 x 10.5 square

= 22/7 x 110.25

= 346.5 cm square

So,area of second circle is 4 time of 346.5 cm

So, area = 4 x 346.5 cm square

= 1386 cm square

Therefore,

22/7 x r square = 1386

R square = 1386 x 7/22

R square = 441

R = 441 under root

R = 21

So, radius of the first circle = 21 cm

So, Circumference = 2 x pi x Radius

= 2 x 22/7 x 21

= 132 cm

So, Circumference of the circle = 132 cm

Step-by-step explanation:

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