A) \[\frac{1}{2}\sqrt{{{\text{v}}_{1}}{{\text{v}}_{2}}}\]
B) \[\frac{{{\text{v}}_{1}}+{{\text{v}}_{2}}}{2}\]
C) \[\frac{2{{\text{v}}_{1}}{{\text{v}}_{2}}}{{{\text{v}}_{1}}+{{\text{v}}_{2}}}\]
D) \[\frac{\text{5}{{\text{v}}_{1}}{{\text{v}}_{2}}}{\text{3}{{\text{v}}_{1}}+2{{\text{v}}_{2}}}\]
Correct Answer: D
Solution :
\[\text{Average speed=}\frac{\text{Total distance travelled }}{\text{Total time taken}}\] \[\text{=}\frac{x}{\frac{2x/5}{{{v}_{1}}}+\frac{3x/5}{{{v}_{2}}}}=\frac{5{{v}_{1}}{{v}_{2}}}{3{{v}_{1}}+2{{v}_{2}}}\]
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