Question 1 Report
The diagram shows a circle with centre \(O\) and radius \(6.5\) cm.
Write down the length of the diameter of this circle.
The diameter of a circle is the straight line through the centre joining two points on the circumference, and it is made of two radii placed end to end. So the diameter is always twice the radius.
\[ d=2r=2\times 6.5=13 \]
The diameter is \(13\) cm [B1].
No \(\pi\) is involved here. The constant \(\pi\) only appears once a curved length or an area is required, such as the circumference \(\pi d\) or the area \(\pi r^2\). The command word "write down" also signals that no calculation is expected beyond the doubling.
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