If the diameter of a circle is increased by 100% , its area is increased by :

Answer: 300%

1. Original area = π × (d/2)² = πd²/4.

2. If diameter is increased by 100%, new diameter = 2d, so new area = π × (2d/2)² = πd² = 4 × (πd²/4).

3. The area becomes 4 times the original, so the increase = 4 − 1 = 3 times the original.

4. Percent increase = 3 × 100% = 300%

Therefore the area is increased by 300%.