Work Step by Step
Since $18=20-2$ and $22=20+2$, then $18 \times 22 = (20-2)(20+2)$. Use the formula $(a-b)(a+b)=a^2-b^2$ with $a=20$ and $b=2$ to obtain: $=20^2-2^2 \\=400-4 \\=396$
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