A globe is 41.142 feet in diameter. Find its exact circumference (distance around) and then approximate its circumference using 3.14 for pi.

Do you know the formula for circumference of a circle?

C=2*pie*r

So, plug the numbers into the formula.

Circumference = 2 • π • radius = π • diameter

But I don't know the radius only the diameter

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Originally Posted by TL3687

but i don't know the radius only the diameter

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What is the relationship of the diameter to the radius?

Attachment 44286

Also, Circumference = π • diameter

So your saying that pie times 41.142 id the exact circumference?

Quote:

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Originally Posted by TL3687

so your saying that pie times 41.142 id the exact circumference?

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apple pie or cherry pie?

It's pi = 3.14.

Circumference = π • diameter
Circumference = 3.14 times the diameter

Okay thank you

So the circumference is 129.251404954

Your instructions are: Find its exact circumference (distance around) and then approximate its circumference.

Quote:

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Originally Posted by TL3687

so the circumference is 129.251404954

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I didn't get that. I got 129.18588.

Just did it on an online calculator = 129.18588

There are two parts to this. First part is to find its "exact"circumference. This part is a trick question - it's impossible to write it out exactly because pi is an irrational number of infinite length, so the "exact" answer would have an infinite number of digits. However, given the fact that you are give the diameter to five significant digits the "best" answer would also have five significant digits, or 129.25. Tacking on more digits than that gives a false sense of accuracy, given that you only know the diameter to 5 decimals.

The second part is to use an estimate of pi of 3.14. Judy gave an answer already, but the answer should be truncated to only 3 decimals given that the estimate of pi that was used is good to only three decimals. So 129 is the right answer.

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Originally Posted by ebaines

The second part is to use an estimate of pi of 3.14. Judy gave an answer already, but the answer should be truncated to only 3 decimals given that the estimate of pi that was used is good to only three decimals. So 129 is the right answer.

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I'm not Judy, and he was told to use pi = 3.14. There are TWO parts to the answer.