Easy -1.2 This is a straightforward algebraic rearrangement requiring only basic manipulation: multiply both sides by 3, divide by π(a+b), then take a square root. It's simpler than average A-level questions as it involves no problem-solving or conceptual understanding beyond routine algebraic skills, though the presence of multiple variables and a square root prevents it from being trivial.
\(r = \sqrt{\frac{3V}{\pi(a+b)}}\) oe www as final answer
3
M1 for dealing correctly with 3; and M1 for dealing correctly with \(\pi(a + b)\), ft; and M1 for correctly finding square root, ft their \(r^2 =\) '; square root symbol must extend below the fraction line
[3]
$r = \sqrt{\frac{3V}{\pi(a+b)}}$ oe www as final answer | 3 | M1 for dealing correctly with 3; and M1 for dealing correctly with $\pi(a + b)$, ft; and M1 for correctly finding square root, ft their $r^2 =$ '; square root symbol must extend below the fraction line | M0 if triple-decker fraction, at the stage where it happens, then ft; condone missing bracket at rh end; M0 if $\pm ...$ or $r > ...$; for M3, final answer must be correct
[3]
Rearrange the following formula to make $r$ the subject, where $r > 0$.
$$V = \frac{1}{3}\pi r^2(a + b)$$ [3]
\hfill \mbox{\textit{OCR MEI C1 2013 Q4 [3]}}