Question

(5) Find the double of the number and fill in the circle​

Answer 1

Answer:

Doubling the diameter is effectively doubling the radius; r = ½(diameter).

Area of a circle is a function of square of the radius.

f(r) = πr²

When radius is doubled; f(2r) = π(2r)² = 4πr²; area increases four times.

When radius is trebled; f(3r) = π(3r)² = 9πr²; area increases nine times.

When radius increases n times; f(nr) = π(nr)² = n²πr²