The U.S. quarter has a mass of 5.67 g and is approximately 1.55 mm thick. How many quarters would have to be stacked to reach 575 ft, the height of the Washington Monument?

**Answer:** 1.13 x 10^5 quarters.

## Explanation

- Begin with the height in feet.
- Use a conversion factor to convert feet into inches.
- Use a conversion factor to convert inches into centimeters.
- Use a conversion factor to convert centimeters into meters.
- Use a conversion factor to convert meters into millimeters.
- Use the thickness per quarter as a conversion factor to convert millimeters into the number of quarters.