Easy -1.8 This is a straightforward rearrangement requiring only basic algebraic manipulation (multiply by 3, divide by πh, then square root). It's simpler than typical A-level questions as it involves no problem-solving, just mechanical application of inverse operations with no quadratic equation to solve.
2 marks for \(r^2 = \dfrac{3V}{\pi h}\) or \(r = \sqrt{\dfrac{V}{\frac{1}{3}\pi h}}\) o.e.; or for correct constructive first step; or for \(r = \sqrt{k}\) ft their \(r^2 = k\)
Total: 3 marks
## Question 16:
$[r] = [\pm]\sqrt{\dfrac{3V}{\pi h}}$ o.e. 'double-decke' | 3 marks | 2 marks for $r^2 = \dfrac{3V}{\pi h}$ or $r = \sqrt{\dfrac{V}{\frac{1}{3}\pi h}}$ o.e.; or for correct constructive first step; or for $r = \sqrt{k}$ ft their $r^2 = k$
**Total: 3 marks**
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16 The volume of a cone is given by the formula $V = \frac { 1 } { 3 } \pi r ^ { 2 } h$. Make $r$ the subject of this formula.
\hfill \mbox{\textit{OCR MEI C1 Q16 [3]}}