Revolutions and diameter question?

Question

1) The diameter of the tire is 2.5 ft. An automobile tire is rated to last for 50000 miles. Estimate the number of revolutions the tire will make in its lifetime. Answer in units of rev.

2) The base of a pyramid covers an area of 26.7 acres (1 acre=43, 560 ft^2) and has a height of 69 ft. If the volume= (1/3)bh, where b is the area of the base and h is the height, find the volume of this pyramid in cubic METERS.

*Yes, I worked it out, but I keep ending up with 8.15x10^6 for the second., and something different every time for the first

Answer 1

1. 1 revolution = circumference = pi x d = 7.854

total distance = 50,000 x 5280 feet = 264 million

total revs = 264 million / 7.854 = 33613523.98

Answer 2

The circumference is roughly 7.85 ft

50k miles is 2.6e+8 ft

dividing, 2.6e+8 ft / 7.85 = 3.3e7 revolutions

2) 26.7 acres = 108000 m²

69 ft = 21 meters

V = (1/3)bh = (1/3) 108000*21 = 756000 m³

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