A) \[75\text{ }km/hr\]
B) \[72\text{ }km/hr\]
C) \[70\text{ }km/hr\]
D) \[30\text{ }km/hr\]
Correct Answer: B
Solution :
Average speed \[=\frac{Total\text{ }distance\text{ }covered}{Total\text{ }time\text{ }taken}\] Let x be the distance between P and Q. Thus, time taken by bus from P to \[Q\,({{t}_{1}})=\frac{x}{60}\] Time taken by bus from Q to \[P({{t}_{2}})=\frac{x}{60}\] Total distance covered = 2x and total time taken \[={{t}_{1}}+{{t}_{2}}\] \[\therefore \] Average speed \[=\frac{2x}{\frac{x}{60}+\frac{x}{90}}\] \[=\frac{2\times 60\times 90}{150}=72\,km/hr\]
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