Question : Find the average speed of a boy if he walks $\frac{1}{6}$th distance with a speed of 5 km/hr and rides a bike to cover the remaining distance at a speed of 25 km/hr. The total distance is 60 km.
Option 1: 15 km/hr
Option 2: 20 km/hr
Option 3: 12 km/hr
Option 4: 13 km/hr
Correct Answer: 15 km/hr
Solution :
Given: A boy walks $\frac{1}{6}$th distance with a speed of 5 km/hr and rides a bike to cover the remaining distance at a speed of 25 km/hr.
The total distance is 60 km.
The distance covered on foot = $\frac{60}{6}$ = 10 km
The distance covered on bike = 60 – 10 = 50 km
The total time taken = $\frac{10}{5}$ + $\frac{50}{25}$ = 2 + 2 = 4 hours
So, the average speed $=\frac{\text{Total distance}}{\text{Total time}}=\frac{60}{4} = 15$ km/hr
Hence, the correct answer is 15 km/hr.
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