A) 5 km/hr.
B) 5. 2 km/hr.
C) 5.5 km/hr.
D) 4.8 km/hr.
Correct Answer: D
Solution :
Let the distance of school from house is x km. \[\therefore \] time taken going to school \[=\frac{x}{6}\,\,h,\] time taken returning from school \[=\frac{x}{4}h\]. \[\therefore \] average speed \[=\frac{~total\text{ }distance}{total\text{ }time\text{ }taken}\] \[=\frac{2x}{\left( \frac{x}{4}+\frac{x}{6} \right)}km/h\] \[=\frac{2x}{\left( \frac{3x+2x}{12} \right)}km/h\] \[=\frac{2x\times 12}{5x}km/h\] \[=\frac{24}{5}km/h=4.8km/h\]
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