Question

Find the diameter of each of the following circles whose areas are given.

(1) 1386 sq cm
(2) 346.5 sq cm
(3) 3850 sq m
(4) 301.84 sq m
(5) 24.64 sq m

Answer 1

(1) Area of the circle is 1386 sq cm.
Area = πr²
1386 sq cm = πr² $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r² = 441cm
r = 21 cm
d = 2 × r
∴ Diameter of the circle = 42 cm.

(2) Area of the circle is 346.5 sq cm.
Area = πr²
346.5 sq cm = πr² $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r² = 110.25 cm
r = 10.5 cm
d = 2 × r
∴ Diameter of the circle = 21 cm

(3) Area of the circle is 3850 sq m.
Area = πr²
3850 sq m = πr² $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r² = 1225 m
r = 35 m
d = 2 × r
∴ Diameter of the circle = 70 m

(4) Area of the circle is 301.84 sq m.
Area = πr²
301.84 sq m = πr² $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r² = 96.04 m
r = 9.8 m
d = 2 × r
∴ Diameter of the circle = 19.6 m

(5) Area of the circle is 24.64 sq m.
Area = πr²
24.64 sq m = π $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r² = 7.84 m
r = 2.8 m
d = 2 × r
∴ Diameter of the circle = 5.6 m