Question

In 2007, the U.S. national debt was about $9 trillion. dollar bill is about 15.5 cm long. If nine 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.)

Answer 1

To calculate the number of times the nine trillion dollar bills would encircle the Earth's equator, we need to find the total length of the dollar bills and divide it by the circumference of the Earth.

Step-by-step explanation:

To calculate the number of times the nine trillion dollar bills would encircle the Earth's equator, we need to find the total length of the dollar bills and divide it by the circumference of the Earth. The length of one dollar bill is given as 15.5 cm. The circumference of the Earth's equator is 2πr, where r is the radius of the Earth at the equator. Converting the radius from kilometers to centimeters, we get 6378 km × 100,000 cm/km = 637,800,000 cm. So, the circumference of the Earth's equator is 2π × 637,800,000 cm. Dividing the total length of the dollar bills (9 trillion × 15.5 cm) by the circumference of the Earth's equator, we can find how many times they would encircle the planet.

Calculating: 9 trillion dollar bills × 15.5 cm = 139.5 trillion cm.
Circumference of Earth's equator = 2π × 637,800,000 cm.
Number of times the dollar bills would encircle Earth = (139.5 trillion cm) ÷ (2π × 637,800,000 cm).

Substituting the values:
Number of times the dollar bills would encircle Earth ≈ (139500000000000 cm) ÷ (2π × 637800000 cm) ≈ 347.34.
Therefore, the nine trillion dollar bills would encircle the Earth's equator approximately 347 times.

Learn more about Circumference of Earth's Equator