A man walks on a straight road from his home to a market 2.5 km away with a speed of 5 km/h.Finding the market closed, he instanly turns and walks back home with a speed of 7.5 km/h.The average speed of the man over the interval of time 0 to 40 min is equal to___________
A. 5 km/h
B. 25/4 km/h
C. 30/4 km/h
D. 45/8 km/h
Answer:D
A man walks on a straight road from his home to a market 2.5 km away with a speed of 5 km/h.Finding the market closed, he instanly turns and walks back home with a speed of 7.5 km/h.The average speed of the man over the interval of time 0 to 40 min is equal to___________
A. 5 km/h B. 25/4 km/h C. 30/4 km/h D. 45/8 km/h