<p>The illumination, $I$ units, of a bulb varies inversely as the square of the distance, $d$ metres.</p>
<p>Given that the illumination is $9$ units when the distance is $2$ m,</p>
<ol class="abc-list"><li><div class="list-item-paragraph">express $I$ in terms of $d$,</div></li><li><div class="list-item-paragraph">find the percentage change in the illumination of the bulb which is required to reduce the distance of the bulb to $\frac{1}{5}$ of its original value.</div></li></ol>

The illumination, $I$ units, of a bulb varies inversely as the square of the distance, $d$ metres.

Given that the illumination is $9$ units when the distance is $2$ m,

find the percentage change in the illumination of the bulb which is required to reduce the distance of the bulb to $\frac{1}{5}$ of its original value.

Inverse Proportion: Illumination and Distance Squared

Inverse Proportion: Illumination and Distance Squared

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