WAEC 2019 · Paper 1 · Q17

Indices & standard form

If $(0.25)^y = 32$ , find the value of $y$ .

Worked solution (try it first)

$0.25 = \frac14 = 2^{-2}$ , so $(0.25)^y = 2^{-2y}$ .
$32 = 2^5$ , so $2^{-2y} = 2^5$ and $-2y = 5$ .
Divide by $-2$ : $y = -\frac52$ , option A.

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