Question

Dr.Ott can run a marathon (26.22 miles) in 2.925 hours. what is his average speed in miles per second?

Answer 1

Use dimensional analysis:

26.22mi/2.925hr * 1hr/3600s = 2.493x10^-3 mi/s

Answer 2

Notice how multiplying by 1hr/3600s allows you to cancel out hours in the denominator and replace it with seconds.