If the diameter of a circle is quadrupled, the circle's area goes up 16 times as area is proportional to diameter squared. Remember area = pi /4 times diameter squared
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In any ratio of shapes: whatever the ratio of the lengths, the ratio of the areas is the square of that ratio.
In this case, the ratio is 1:4, so the areas are in the ratio of 1²:4² = 1:16; ie as the length of the diameter is quadrupled (ratio 1:4), the area becomes 16 times bigger (1:16).
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As the area of a circle A equals pi times the radius squared, and doubling the diameter means multiplying the radius by four, the area is multiplied by 16 when you double the diameter.
When the diameter of the circle doubled, its circumference also doubled.However, its area increased to 4 times the original area, while nobody was looking.
The area of a circle with the diameter of 3m is 7.069 m2
The area of a circle with diameter of 4.9 is 75.43 units2
The diameter of a circle whose area is 200.96 is: 16