The U.S. quarter has a mass of 5.67 g and is approximately 1.55 mm thick, (a) How many quarters would have to be stacked to reach 575 ft, the height of the Washington Monument? (b) How much would this stack weigh? (c) How much money would this stack contain? (d) The U.S. National Debt Clock showed the outstanding public debt to be $16,213,166,914,811 on October 28, 2012. How many stacks like the one described would be necessary to pay off this debt?

Solution 69AE: (a) Here we need to find out the number of quarters required to be stacked to reach 575 ft, the height of the Washington Monument Step 1: Conversion of the height mm to ft We know, 1 inch = 2.54 cm 1 cm =10 mm Therefore 1 in = 25.4 mm 1 ft = 12 in The thickness of the quarter is 1.55 mm = 1.55 mm x 1 in x 1 ft= 0.00508 ft 25.4 mm 12 in Thus the thickness of the quarter is 0.0051 ft