SOLUTION: The diameter of a penny is about 1.9 x 10^-5 km. It would take about 2.1 x 10^9 pennies placed end to end to circle the equator once. What is the approximate length of the equator?

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Question 720351: The diameter of a penny is about 1.9 x 10^-5 km. It would take about 2.1 x 10^9 pennies placed end to end to circle the equator once. What is the approximate length of the equator?
I think this is a division problem, I appreciate any help

Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


Let's see if your idea makes any sense. If it is a division problem we either have to divide the diameter of a penny, order of magnitude 10^-5 km, by the number of pennies that go around the equator, order of magnitude 10^9, getting an answer of order of magnitude 10^-14 km, roughly 100,000 times smaller than a human hair. Nope.

Or we have to divide 10^9 by 10^-5, making 10^14 km which is roughly the diameter of our entire solar system out to the outer planets. Nope.

Let's multiply: 2.1 X 10^9 times 1.9 X 10^-5 = 4.0 X 10^4 or about 40,000 km, which is about 24,900 miles. Very close to Eratosthene's result circa 240 BCE.

John

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