SmarterEd

Aussie Maths & Science Teachers: Save your time with SmarterEd

Equations, SM-Bank 067

Find the value of  \(\large r\) in the formula \(A=\pi r^2\) given \(A=10\). Assume  \(\large r\) is positive and give your answer correct to 1 decimal place.  (2 marks)

Show Answers Only

\(r\approx 1.8\)

Show Worked Solution
\(A\) \(=\pi r^2\)
\(\pi r^2\) \(=10\)
\(r^2\) \(=\dfrac{10}{\pi}\)
\(\sqrt{r^2}\) \(=\sqrt{\dfrac{10}{\pi}}\)
\(r\) \(=1.784\ldots\)
  \(\approx 1.8\ (1\text{ d.p.})\)