Multiple choice

The radius of a circle is stated as $2.12\ cm$. Its area should be written as

  1. $14\ cm^{2}$
  2. $14.1\ cm^{2}$
  3. $14.11\ cm^{2}$
  4. $14.1124\ cm^{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Area = pi * r^2. Using pi = 3.14159 and r = 2.12, Area = 3.14159 * 4.4944 = 14.119. Significant figures: the radius 2.12 has 3 significant figures, so the result should be rounded to 3 significant figures, which is 14.1.

AI explanation

The given radius has three significant digits, so the calculated area must also be rounded to three significant digits. Using the area of a circle formula, we multiply pi by 2.12 squared to get 14.1124. Rounding 14.1124 to three significant digits gives 14.1. The area is 14.1 sq. cm.

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