The US. quarter has a mass of 5.67 g and is approximately 1.55 mm thick (a) How many quarters would have to bestacked to reach 575 ft, the height of the Washington Monument? (b) How much would this stack weigh? (c) How muchmoney would this stack contain? (d) The US. National Debt Clock showed the outstanding public debt to be516.213.166.914,811 on October 28, 2012 How many stacks like the one described would be necessary to pay off this debt?

a) 113,071 quarters

b) 641 kg

c) $28,267.75

d) 18,261,558.4 stacks

Explanation:

a) 1 ft is equivalent to 304.8 mm, thus 575 ft = 175260 mm

So, the quantity of quarters needed is the height divided by the height of the quarter (its thickness):

175260/1.55 = 113,070.9677 = 113,071 quarters.

b) If one quarter has 5.67g, thus the total mass is the number of quarters multiplied by 5.67:

113,071 * 5.67 = 641,112.57 g = 641 kg

c) One quarter is equal to $ 0.25, thus it's value is the number of quarters multiplied by 0.25:

113,071 * 0.25 = $28,267.75

d) If one stack corresponds to $28,267.75, thus the number of stacks will be the debt divided by it:

516,213,166,914.811/28,267.75 = 18,261,558.4 stacks.