Area, SM-Bank 124

Calculate the area of the following composite shape, giving your answer correct to one decimal place. (2 marks)

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\(321.0\ \text{cm}^2\ (1 \text{ d.p.})\)

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\(\text{Radius small semi-cirle}(r)=4.5\ \text{mm}\)

\(\text{Radius large semi-cirle}(R)=9\ \text{mm}\)

\(\text{Total area}=\text{Area small semi-cirle}+\text{Area large semi-cirle}+\text{Area rectangle}\)

\(A\)	\(=\dfrac{1}{2}\times \pi r^2+\dfrac{1}{2}\times \pi R^2+lb\)
	\(=\dfrac{1}{2}\times \pi\times 4.5^2+\dfrac{1}{2}\times \pi\times 9^2+18\times 9\)
	\(=31.808\dots+127.234\dots+162\)
	\(=321.043\dots\approx 321.0\ \text{cm}^2\ (1 \text{ d.p.})\)