Length of DNA strand

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The DNA molecule has a double helix structure. The radius of each helix is approximately $10$ angstroms ($1$ angstrom $=10^{-8}$cm). Each helix goes up by approximately $34$ angstroms every revolution, and there are about $2.9\times10^8$ revolutions. Estimate the total arc length of each helix (that is the length of the helix when it is unravelled).

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Hint: As the travel along the helix is perpendicular to the travel around the circle, you can use Pythagoras' theorem to compute the length of one turn of the helix. Alternately, you can think of unrolling the cylinder that the helix is on. You might experiment with the cardboard core of a roll of paper towels or toilet paper to get some intuition.