Find the circumference of the circle whose area is 16 times the area of the circle with diameter 7 cm.

Let area of larger circle be r cm. Radius of circle with diameter 7 cm = = 3.5 cm. Given, Area of larger circle is 16 times the area of the circle with diameter 7 cm. ⇒ πr 2 = 16 x π x (3.5) 2 ⇒ r 2 = 196 ⇒ r = = 14 cm. Circumference = 2πr = = 88 cm. Hence, circumference of circle = 88 cm.