Mary starts from her house, walks 80 meters south, and stops to chat with her aunt on the sidewalk. after chatting for a few minutes, she walks 125 meters to the west to meet a friend and then walks 45 meters north with her friend to a cafe for lunch. overall, she takes 10 minutes to do all this. what is mary’s average speed?

8 meters/second
1.25 meters/second
25 meters/second
4.5 meters/second
0.42 meters/second

0.42 meters/second

Explanation:

The total distance traveled by Mary is: 80 m + 125 m + 45 m = 250 m  

We want the speed in meters/second, so we have to convert the 10 minutes elapsed during the trip into seconds. Then we need a conversion factor, 1 minute is equivalent to 60 seconds.

time = 10 minutes * (60 seconds/1 minute) = 600 seconds (notice that minute is cancelled because is multiplying and dividing)

Now, we can compute the average speed is as follows:

Average speed = total distance/time = 250 m/600 s =  0.42 m/s

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