Twice the diameter also means the radius is twice of the smaller circle. The ratio is the same since diameter is divided by 2 to get radius.

When you divide all quantities in a ratio by the same factor, the ratio remains the same.

(Eg. If the diameters are 12cm and 6cm respectively, the radii are 6cm and 3cm. One is still twice of the other. Ratio is still 2 : 1)


Formula for area of circle is : π r²

Since the radius is twice of the smaller circle, the bigger circle's area will be :

π x (2 x radius of smaller circle) x (2 x radius of smaller circle)

= 4 x π x radius of smaller circle x radius of smaller circle

= 4 x area of smaller circle

Could u just write out all the working and ans

So the bigger circle area is 4 times of the smaller circle.

Shaded area = bigger circle - smaller circle
= 3 times of smaller circle.

The above explanation is sufficient for you to derive the answer. It is easy enough.

What's the area of bigger circle?

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