A) 9 km/h
B) 4.5 km/h
C) 4 km/h
D) 3 km/h
Correct Answer: C
Solution :
If the same distances are covered at different speeds of x km/h and y km/h, the average speed of the whole journey is given by\[=\frac{2xy}{x+y}\,\,\text{km/h}\text{.}\] \[\therefore \] Required average speed \[=\frac{2\times 6\times 3}{6+3}=\frac{36}{9}=4\,\,\text{km/h}\]
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