J & K CET Engineering J and K - CET Engineering Solved Paper-2014

  • question_answer
    A car moving on a straight road covers \[1/3\] of the distance with \[25\text{ }km/h\] and rest with'\[75\text{ }km/h\]. The average speed is

    A)  \[25\text{ }km/h\]          

    B)  45 km/h

    C)  \[55\text{ }km/h\]          

    D)  \[~75\text{ }km/h\]

    Correct Answer: B

    Solution :

    \[={{V}_{aV}}=\frac{Total\text{ }distance\text{ }covered}{Total\text{ }time\text{ }taken}\] \[=\frac{\frac{x}{3}+\frac{2x}{3}}{{{t}_{1}}+{{t}_{2}}}\] [Let the total distance covered is x km] \[=\frac{\frac{x}{3}+\frac{2x}{3}}{\frac{\left( \frac{x}{3} \right)}{25}+\frac{\left( \frac{2x}{3} \right)}{75}}\] \[=\frac{x}{\frac{x}{75}+\frac{2x}{225}}=\frac{x}{\frac{(3+2)x}{225}}\] \[=\frac{225}{5}=45m/s\]


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