39. Folding paper. Each time you fold an ordinary sheet of paper in half, you double the thickness.

a. A single sheet of 20-pound bond paper is about a tenth of a millimeter

thick. How would you come up with this estimate? (Hint: Paper often

comes in reams of 500 pages.)

b. Find an exponential formula that gives the thickness of the sheet of paper

in part a after

f

folds in millimeters and in kilometers.

c. What would be the thickness in kilometers if you were physically able to

fold it 50 times? Note: For comparison, the distance from Earth to the Sun

is about

149,600,000

kilometers.