JAMB 2010 · UTME · Q17

Variation

If $y$ varies directly as the square root of $x$ and $y = 3$ when $x = 16$ , calculate $y$ when $x = 64$ .

Worked solution (try it first)

$y = k\sqrt x$ .
Put in $y = 3$ , $x = 16$ : $3 = 4k$ , so $k = \frac34$ .
When $x = 64$ : $y = \frac34 \times 8 = 6$ , option C.

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