Question

The circumference of a circle exceeds the diameter by 21 cm. Find the area of a circle​

Answer 1

Answer:

Step-by-step explanation:

Circumference = d + 21

2 π d/2 = d + 21

π d = d + 21

π d - d = 21

d ( π - 1 ) = 21

d = 21/ 22/7-1

d = 21 x 7/ 22-7

d = 9.8 cm

r = 4.9 cm

Area of circle = π r²

= 22/7 x 4.9 x 4.9

Area of circle = 75.46 cm²

Answer 2

Let the diameter be 2r

now circumference of circle exceeds the diameter by 21 means using formula circumference of circle we get,

$2 \pi \: r = 21 + 2r$
$2 \times \frac{22}{7} \times r - 21 = 2r$
$\frac{44r}{7} - 21 = 2r$
$\frac{44r - 147}{7} = 2r$
$44r - 147 = 14r$
$30r = 147$
$r = \frac{147}{30}$
$r = 4.9cm$

Now use formula are of circle u will get answer 79.39cm^2