A) 25 km/h
B) 45 km/h
C) 55 km/h
D) 75 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] \[=\frac{\frac{x}{3}+\frac{2x}{3}}{\frac{\left( \frac{x}{3} \right)}{25}+\frac{\left( \frac{2x}{3} \right)}{75}}\] \[=\frac{x}{\frac{x}{75}+\frac{2x}{225}}=\frac{x}{\frac{(3+2)x}{225}}\] \[=\frac{225}{5}=45\,m/s\]
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