Question

The radius of a circle is stated as 2.12 cm. Its area should be written as
(a) 14 cm²
(b) 14.1 cm²
(c) 14.11 cm²
(d) 14.1124 cm²

Answer 1

(b) 14.1 cm²

Area of a circle, A = $\pi r^2$
On putting the values, we get:

$$\begin{gathered} A=\frac{22}{7}\times 2.12\times 2.12 \\ \Rightarrow A=14.1{\mathrm{cm}}^2 \end{gathered}$$

The rules to determine the number of significant digits says that in the multiplication of two or more numbers, the number of significant digits in the answer should be equal to that of the number with the minimum number of significant digits. Here, 2.12 cm has a minimum of three significant digits. So, the answer must be written in three significant digits.