JAMB 2013 · UTME · Q15

Variation

If $r$ varies inversely as the square root of $s$ and $t$ , how does $s$ vary with $r$ and $t$ ?

Worked solution (try it first)

$r = \dfrac{k}{\sqrt{st}}$ .
Square both sides: $r^2 = \dfrac{k^2}{st}$ .
Make $s$ the subject: $s = \dfrac{k^2}{r^2t}$ .
So $s$ varies inversely as $r^2$ and $t$ , option D.

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