[TL3687]

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

[Wondergirl]

Do you know the formula for circumference of a circle?

[TL3687]

C=2*pie*r

[Wondergirl]

So, plug the numbers into the formula.

Circumference = 2 • π • radius = π • diameter

[TL3687]

But I don't know the radius only the diameter

[Wondergirl]

but i don't know the radius only the diameter

What is the relationship of the diameter to the radius?

Also, Circumference = π • diameter

[TL3687]

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

[Wondergirl]

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

apple pie or cherry pie?

It's pi = 3.14.

Circumference = π • diameter
Circumference = 3.14 times the diameter

[TL3687]

Okay thank you

[TL3687]

So the circumference is 129.251404954

[Wondergirl]

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

[Wondergirl]

so the circumference is 129.251404954

I didn't get that. I got 129.18588.

Just did it on an online calculator = 129.18588

[ebaines]

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.

[Wondergirl]

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.

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