Dora walked 3 kilometers. She walked first 1.5 kilometers in 20 meter per sec and the rest 1.5 kilometers in 60 meter per sec. what is the average speed? Choose one:
A) 28m/s
B) 30m/s
C) 32m/s
D) 34m/s
E) 36m/s
Since the distance traveled is same, we can apply direct formula= 2XS1XS2/(S1+S2)   2X20X60/80= 30. '30m/s' is the answer.
<result>B</result>
Dora walked 3 kilometers. She walked first 1.5 kilometers in 20 meter per sec and the rest 1.5 kilometers in 60 meter per sec. what is the average speed?