Question : A boy goes from home to school at a speed of 30 km/hr and returns back at a speed of 70 km/hr. What is his average speed for the journey?
Option 1: 42 km/hr
Option 2: 48 km/hr
Option 3: 38 km/hr
Option 4: 36 km/hr
Correct Answer: 42 km/hr
Solution :
Given: Going speed = 30 km/hr
Returning speed = 70 km/hr
We know that,
$\text{Average speed} =\frac{2S_1S_2}{S_1+S_2}=\frac{2×30×70}{30+70}=42$ km/hr
Hence, the correct answer is 42 km/hr.
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