Question

..10 The circumference of a circle is 123.2 cm. Calculate :
(i) the radius of the circle in cm.
(ii) the area of the circle in cm2, correct to the nearest cm2.
(iii) the effect on the area of the circle if the radius is doubled.​

Answer 1

Step-by-step explanation:

circumference of circle = 2πr = 123.2

$2\pi \: r = 123.2 \\ 2 \times \frac{22}{7} \times r = 123.2 \\ r = \frac{123.2 \times 7}{22 \times 2} \\ r = \frac{61.6 \times 7}{22} \\ r = 2.8 \times 7 \\ r = 19.6$

radius of circle = 19.6 cm

area of circle = πr^2

$= \frac{22}{7} \times 19.6 \times 19.6 \\ = 22 \times 19.6 \times 2.8 \\ = 1207.36 \: {cm}^{2}$

area of circle = 1207.36 sq cm

if radius is double r = 2 × 19.6 = 39.2 cm

area will be

$= \frac{22}{7} \times 39.2 \times 39.2 \\ = 22 \times 39.2 \times 5.6 \\ = 4829.44 \: {cm}^{2}$

the ratio of area

1207.36 : 4829.44

1 : 4

therefore if the radius is doubled the area increases 4 times

hope you get your answer

Answer 2

hope you understood if not tell me