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In terms of radius r, the circumference is:
Api r sq
B4 pi r
Cpi r by 2
D2 pi r
Answer & Solution
Correct answer: D. 2 pi r
1. The diameter of a circle is twice its radius.
2. The circumference is pi times the diameter.
3. So the circumference is 2 pi r.
4. The answer is 2 pi r.
_Source: NCERT Class 9 Mathematics, Ch 6 'Measuring Space: Perimeter and Area'_
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