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Area, SM-Bank 119

Calculate the area of a semi-circle with a diameter of 60 centimetres. Give your answer correct to one decimal place.   (2 marks)

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\(1413.7\ \text{cm}^2\ (1 \text{ d.p.})\)

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\(\text{Diameter}=60\ \text{cm}\)

\(\therefore\ \text{Radius}=30\ \text{cm}\)

\(\text{Area semi-circle}\) \(=\dfrac{1}{2}\times \pi r^2\)
  \(=\dfrac{1}{2}\times \pi\times 30^2\)
  \(=1413.716\dots\)
  \(=1413.7\ \text{cm}^2\ (1 \text{ d.p.})\)

Area, SM-Bank 111

Calculate the area of the following semi-circle, giving your answer as an exact value in terms of \(\pi\).  (2 marks)
 

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\(1250\pi\ \text{m}^2\)

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\(\text{Diameter}=100\ \text{m}\)

\(\therefore\ \text{Radius}=50\ \text{m}\)

\(\text{Area semi-circle}\) \(=\dfrac{1}{2}\times\pi r^2\)
  \(=\dfrac{1}{2}\times\pi\times 50^2\)
  \(=1250\pi\ \text{m}^2\)

Area, SM-Bank 110

Calculate the area of the following semi-circle, giving your answer to 2 decimal places.   (2 marks)
 

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\(0.57\ \text{mm}^2\ (2\ \text{d.p.})\)

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\(\text{Diameter}=1.2\ \text{mm}\)

\(\therefore\ \text{Radius}=0.6\ \text{mm}\)

\(\text{Area semi-circle}\) \(=\dfrac{1}{2}\times\pi r^2\)
  \(=\dfrac{1}{2}\times\pi\times 0.6^2\)
  \(=0.5654\dots\)
  \(\approx 0.57\ \text{mm}^2\ (2\ \text{d.p.})\)

Area, SM-Bank 109

Calculate the area of the following semi-circle, giving your answer to 2 decimal places.   (2 marks)
 

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\(173.18\ \text{m}^2\ (\text{2 d.p.})\)

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\(\text{Diameter}=21\ \text{m}\)

\(\therefore\ \text{Radius}=10.5\ \text{m}\)

\(\text{Area semi-circle}\) \(=\dfrac{1}{2}\times\pi r^2\)
  \(=\dfrac{1}{2}\times\pi\times 10.5^2\)
  \(=173.1802\dots\)
  \(\approx 173.18\ \text{m}^2\ (2\ \text{d.p.})\)