Find the areas of circle 1 and circle 2.How many copies of circle 1 would you nee to equal the area of circle 2?

Question

Circle 1 has a diameter of 4 mi

 

 

Circle 2 has a diameter of 12 mi

Answer 1

Area = pi * radius ^2

The area of circle #1 is pi * 2^2 = pi * 4 <---- notice the diameter is given as 4 miles, so the radius is 2 mi

The area of circle #2 is pi * 6^2 = pi * 36 <--- again, the diameter is given as 12 miles, so the radius is 6 mi

Dividing these areas:
36*pi
------------- = 9 <---- pi cancels out
4 * pi

So 9 copies of circle #1 shall equal the area of circle #2

 Area = pi * radius ^2

 

 The area of circle #1 is pi * 2^2 = pi * 4 <---- notice the diameter is given as 4 miles, so the radius is 2 mi

 

The area of circle #2 is pi * 6^2 = pi * 36 <--- again, the diameter is given as 12 miles, so the radius is 6 mi

 

 Dividing these areas:

      36*pi

-------------  =   9   <---- pi cancels out

       4 * pi

 

So 9 copies of circle #1 shall equal the area of circle #2