2. How many times can a bill be folded before it wears out

From carrying around Nigerian parasites to holding onto flu virii for 17 days, notes have been folded, wrinkled and punished throughout their lives.  A U.S currency bank note can survive being folded and unfolded 4,000 times before it's time to take leave from human hands.

The Federal Reserve reports that the average lifespan of a one dollar bill is about 22 months. Two years for the $5 bill, three years for the $10 bill, four years for the $20 bill and nine years for the $50 and $100 bills. Being more durable, coins can last for about 3 decades.

3. Coins and the Newton Connection

People assume ridges are designed into coins for better grip and to help the blind easily tell coins apart by feel. In the early days when coins were made of gold or silver, unscrupulous people would file away at the edge to collect the precious metals.

Sir Isaac Newton proposed creating ridges or grooves axially along the circumference, this would make it very apparent to the receiver of the coin if someone has been shaving away along the edge. The trend continued because of the accompanying benefits.