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How do you calculate the circumference of a circle with radius 4 cm?

The circumference of a circle with a radius of 4cm4 \, \text{cm} is given by the expression 8πcm8\pi \, \text{cm}.

To determine the circumference of a circle, we use the formula:

C=2πrC = 2\pi r

where CC denotes the circumference and rr represents the radius of the circle. In this scenario, the radius rr is specified as 4cm4 \, \text{cm}. Substituting this value into the formula yields:

C=2π×4C = 2\pi \times 4

This expression simplifies to:

C=8πC = 8\pi

Thus, the circumference of the circle is 8πcm8\pi \, \text{cm}.

If you require a numerical approximation, you can use π3.14\pi \approx 3.14 (though for greater accuracy, utilizing a calculator for the value of π\pi is recommended). Using this approximation:

C8×3.14=25.12cmC \approx 8 \times 3.14 = 25.12 \, \text{cm}

Therefore, the circumference is approximately 25.12cm25.12 \, \text{cm} when π\pi is rounded to 3.143.14. However, in most GCSE Mathematics problems, it is preferable to present your answer in terms of π\pi, unless otherwise directed. This approach not only simplifies calculations but also enhances precision. Consequently, the exact circumference remains 8πcm8\pi \, \text{cm}.

Answered by: Prof. Michael Lewis
IB Physics Tutor
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