Question

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?

Answer 1

800,000,000 revolutions

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

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