At 60 miles per hour, my car's dashboard shows 4000 rpm. this means that the crankshaft, which drives the car, is turning at 4000 revolutions per minute. if a car went 60 miles per hour for 200,000 miles, how many revolutions would the crankshaft have done?

  800,000,000 revolutions

Step-by-step explanation:

At 60 miles per hour, a car travels 1 mile per minute, so the crankshaft is turning ...

  (4000 revolutions/minute)/(1 mile/minute) = 4000 revolutions per mile

Then in 200,000 miles, it will have turned ...

  (200,000 mi)×(4000 rev/mi) = 800,000,000 rev

In scientific notation, that's 8×10^8 revolutions.