Question

A circle has an area of 12. If the radius is increased by a factor of 2, what is the new area of the circle?

Answer 1

A=12. A=π×r^2(area of a circle)
π×r^2=12
r×2:
π×(r×2)^2= π×r^2×4. Here you can see that the calculation is exactly the same as above except from the Factor 4. This Shows that the area is four times bigger than before: 12×4