The diameter of a bicycle wheel is 2 feet. about how many revolutions does the wheel make to travel 2 kilometers? hint: km ≈ 3, 280 ft

First step is to convert feet to kilometers.  2 kilometers is approximately equal to 6,560 ft.  

Keeping that number in mind, we need to find the circumference of the circle.  We need this number because that is the exact distance the wheel will travel in a single revolution.  We can use the equation c=pi(d) to get it, or use the more commonly cited formula c=2pi(r), with a few added steps.  Since we're given the diameter, not the radius, the first formula makes more sense.

The circumference is roughly equal to 6.28.  That means the bike travels 6.28 feet for every complete revolution.  Since that's 6.28 feet for every SINGLE revolution, we can simply divide the total distance the bike traveled (6560 ft) by the distance which it travels per revolution (6.28).

6560 ft divided by 6.28 ft/1 revolution = 1044.59 revolutions.