richiesmasher
Junior Member
- Joined
- Dec 15, 2017
- Messages
- 111
Hi let's say we have a circle of diameter 15cm, and another circle of diameter 30cm.
Is the second circle 4 times as large, or twice as large.
Using the circumference formula I'll find out that the circumference doubles, but using the area formula I'll see that the area quadruples, so what is the correct thing to say? is the second cirlce twice or four times as large?
Area of circle 1=pi*r2
A1= pi*(d/2)2 = pi*d2/4
Area of circle 2 = pi*2(d2/4) = pi*4d2/4= pi*d2
So the ratio of the areas of the two circles is (d^2)/((d^2)/4)
So that will work out to 4:1
But using the circumference I'll get 2:1
Is the second circle 4 times as large, or twice as large.
Using the circumference formula I'll find out that the circumference doubles, but using the area formula I'll see that the area quadruples, so what is the correct thing to say? is the second cirlce twice or four times as large?
Area of circle 1=pi*r2
A1= pi*(d/2)2 = pi*d2/4
Area of circle 2 = pi*2(d2/4) = pi*4d2/4= pi*d2
So the ratio of the areas of the two circles is (d^2)/((d^2)/4)
So that will work out to 4:1
But using the circumference I'll get 2:1