Question 1
2 marksThe circumference of a circle is 50 cm.
Work out the radius of the circle.
Give your answer correct to 3 significant figures.
Model answer
\(2\pi r = 50\)
\(r = \dfrac{50}{2\pi} = 7.957...\)
7.96 cm (3 s.f.)
Explanation
Write the circumference formula as an equation and rearrange: divide 50 by \(2\pi\). Dividing by π alone gives the diameter, 15.9 cm, so remember to halve it.
Mark scheme
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1 mark
M1 for \(2\pi r = 50\) or \(r = \dfrac{50}{2\pi}\)
or d = 50 ÷ π (= 15.9...)
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1 mark
A1 for 7.96 cm
awrt 7.96 (7.957...); correct answer with no working scores full marks