# What is the area of a semicircle of radius 4r?

$Areaofsemicircle=\frac{{\mathrm{\pi r}}^{2}}{2}\phantom{\rule{0ex}{0ex}}puttingradius=4r\phantom{\rule{0ex}{0ex}}Areaofsemicircle=\frac{\pi {\left(4r\right)}^{2}}{2}=\frac{\mathrm{\pi}\times 4\mathrm{r}\times 4\mathrm{r}}{2}=8{\mathrm{\pi r}}^{2}$

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