Speed of Anil is (\frac{4}{5}) of average speed of Suresh. Suresh goes office from his home in 5 hours with the speed of 12 km per hour and returns in 4 hours with the speed of 15 km/hour. How long will it take for Anil to cover 80 km distance?
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7 hours
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7.5 hours
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8 hours
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12 hours
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None of these
B
Correct answer
Explanation
Suresh travels same distance both ways: 12 × 5 = 15 × 4 = 60 km. Average speed = total distance/total time = 120/9 = 13.33 km/h. Anil's speed = 4/5 × 13.33 = 10.67 km/h. Time for 80 km = 80/10.67 = 7.5 hours. Alternatively, if using weighted average: (60+60)/(5+4) = 120/9 = 13.33 km/h, same result.