| Person went from A to B at an average speed of x km/h and returned from B to A at an average speed of y km/h. What was his average speed during the journey? [SSC (10+2) 2010] |
A) \[\frac{x+y}{2xy}\]
B) \[\frac{2}{x+y}\]
C) \[\frac{2xy}{x+y}\]
D) \[\frac{1}{x}+\frac{1}{y}\]
Correct Answer: C
Solution :
| Average speed\[=\frac{\text{Total}\,\,\text{distance}}{\text{Total}\,\,\text{time}}\] |
| \[=\frac{2}{\frac{1}{x}+\frac{1}{y}}=\frac{2}{\frac{x+y}{xy}}=\frac{2xy}{x+y}\] |
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