Starting from the front door of your ranch house, you walk 55.0 m due east to your windmill, turn around, and then slowly walk 35.0 m west to a bench, where you sit and watch the sunrise. It takes you 30.0 s to walk from your house to the windmill and then 36.0 s to walk from the windmill to the bench. Required:
a. For the entire trip from your front door to the bench, what is your average velocity?
b. For the entire trip from your front door to the bench, what is your average speed?

Explanation:

Average velocity = Total displacement / total time

Average speed = total distance covered / total time

a )

For the entire trip from your front door to the bench

Total displacement = 55 - 35 = 20 m  [ first displacement is positive and second displacement is negative , because second displacement is in opposite direction ]

Total displacement = 20 m

Total time = 30 + 36 = 66 s

Average velocity = 20 / 66

= .303 m / s

b )

For the entire trip from your front door to the bench

Total distance covered  = 55 + 35 = 90  m

Total time = 30 + 36 = 66 s

Average speed  = 90 / 66

= 1.36  m / s

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).