Question

calculate the area of the circle. formula: a = πr² use 3.14 for pi. a = ? cm² round to the nearest tenth.

Explanation:

Step1: Substitute the radius into the formula

Given \( r = 13\) cm and \( \pi=3.14\), substitute into \( A=\pi r^{2}\). So \( A = 3.14\times13^{2}\).

Step2: Calculate \(13^{2}\)

\(13^{2}=13\times13 = 169\). Then the formula becomes \( A=3.14\times169\).

Step3: Multiply the numbers

\(3.14\times169=(3 + 0.14)\times169=3\times169+0.14\times169=507+23.66 = 530.66\).

Step4: Round to the nearest tenth

The digit in the hundredth place is \(6\). Using the rounding rule (if the digit in the hundredth place \( \geq5\), round up the digit in the tenth place), \(530.66\approx530.7\).

Answer:

\(530.7\)