Question 566511: a coffee can is shaped like a cylinder 13cm high.Its base is a circle with diameter of 10 cm. What is the circumference of the base?
Answer by bucky(2189)   (Show Source):
You can put this solution on YOUR website! The fact that the coffee can is 13 cm high is just extra information. You can ignore that because it has nothing to do with finding the circumference of the base.
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The circumference of a circle is found by using one of two formulas. You can use either this first equation:
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in which C is the circumference, r is the radius, and  is the Greek letter pi which is a number with a never ending number of decimal places. The value of pi rounded off to 9 decimal places is 3.141592654
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Or you can use this second equation:
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in which C again is the circumference, d is the diameter, and again pi rounded to 9 decimal places is 3.141592654.
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Since you were given the diameter of the circular base, you can use the second equation directly as follows:
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and since d is given as 10 cm, you can substitute 10 for d to get:
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This is the answer. However, normally we would reverse the two factors on the right side, so we would write the answer as:
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And don't forget that since the units of the diameter is cm, the units for the circumference is also cm.
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If your book or teacher wants you to give your answer in terms of a number, you can substitute 3.141592654 for , and when you multiply that by 10 you get the answer for C as:
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 cm
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So you can say that C is approximately 31.416 cm. which should be more than accurate enough to express the circumference of a coffee can.
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Hope this helps you to understand the problem a little better.
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