waecmaths question:
Simplify, correct to three significant figures, ${{(27.63)}^{2}}-{{(12.37)}^{2}}$
Option A:
614
Option B:
612
Option C:
611
Option D:
610
waecmaths solution:
$\begin{align} & {{(27.63)}^{2}}-{{(12.37)}^{2}}=(27.63-12.37)(27.63+12.37) \\ & {{(27.63)}^{2}}-{{(12.37)}^{2}}=(\text{15}\text{.26})(40) \\ & {{(27.63)}^{2}}-{{(12.37)}^{2}}=\text{610}\text{.4} \\ & {{(27.63)}^{2}}-{{(12.37)}^{2}}\approx 610\text{ (3s}\text{.f)} \\\end{align}$
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