How do you do this?

C. 1

Step-by-step explanation:

Distance between workplace and home  =  45 miles

Time taken to drive from his workplace to home =  30 minutes

The time taken for him to go back home to retrieving his wallet and come back to the workplace is twice as long.

This means if the time for him to go from his workplace to home is 30 minutes,then the time take for him to go from his home to the workplace is 30×2=60 minutes.

The distance is:   2×45  =  90 miles

Time taken :   30 + 60 =  90 minutes

Average speed  =  Distance / Time

  =  90/90

  =  1 minute/mile.

So the average speed is 1 minute/mile

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