If pennies are 1.89 cm in diameter and has a mass of 2.5622g, how much would it cost to cover a roof that is 32ft x 45ft?

Answer by  wasosa (13)

A foot is 12 inches, and one inch is 2.54cm. Therefore, one foot is 30.48cm; the question can thus be reduced to one of division. 32x30.48cm/1.89cm = 516.06 and 45x30.48cm/1.89cm = 725.71 ... so it would cost 516x725 pennies, or $3,741.

Answer by  billhpike (8)

The roof has an area of 1337803.78 sq-cm. The penny area is 2.806. Using the hexagonal packing, circles cover 90.7% of the space, so 431,949 pennies, or $4319.49 are needed.