78. The radius of each wheel of a car is 15 inches. If the wheels are turning at 3 revolutions / second, how fast is the car moving? Express your answer in inches per second and in miles per hour. ""Assuming One mile =5282 feet the car is travelling 16.06mph"" *&*& That would be ( 2 pi * 15 inches) / revolution * 3 revolutions / second * 3600 seconds / hour / ( 5280 ft / mile * 12 in / ft). 16.06 mph is close to my estimate of that result so I imagine you are correct. *&*& 80. The windshield wiper of a car is 18 inches long. If it takes 1 second to trace out 1 / 3 revolution, how fast is the tip of the wiper moving? """ The wiper is moving 2.14mph""" *&*& The calculation would be similar to the above, and I estimate about 2 mph, so you’re probably right here also. *&*& 84. A Ferris wheel has radius 30 feet and makes one revolution in 70 seconds. What is the speed of a point on the outer part of the wheel? """The wheel is moving 1.835mph"" *&*& I estimate about 2.7 ft / sec, which is pretty close to 1.8 mph. Again I believe you’re right. *&*& 90. A nautical mile is the length of the arc subtended by a central angle of 1 minute on a great circle (a circle on the surface of the Earth which divides the Earth into two equal hemispheres). If the radius of the Earth is 3960 miles, express 1 nautical mile in terms of statute miles (a statue mile is 5280 feet). """A nautical mile is one minute of arc = (2*Pi *3960/360)/60 .. Therefore one minute/nautical mile is equal to 1.152miles"" *&*& This also has the ring of truth *&*&