At the time of this book's printing, the U.S. national debt is about 8 trillion. (a) If payments were made at the rate of 1000 per second, how many years would it take to pay off the debt, assuming no interest were charged?...

 17. At the time of this book's printing, the U.S. national debt is about  8 trillion. (a) If payments were made at the rate of  1000 per second, how many years would it take to pay off the debt, assuming no interest were charged?

(b) A dollar bill is about 15.5 cm long. If eight trillion dollar bills were laid end to end around the Earth's equator, how many times would they encircle the planet? Take the radius of the Earth at the equator to be 6378 km. Note:

Before doing any of these calculations, try to guess at the answers. You may be very surprised.