A car runs for the first 375 km at an average speed of 50 km/hr, the next 315 km at an average speed of 70 km/hr and the next 575 km at an average speed of 57.5 km/hr. What is the average speed (in km/hr) for the entire journey?
- AOption (a)
55.5
- BOption (b)
57.5
- COption (c)
66.5
- DOption (d)
62.5
हिंदी में देखें
एक कार पहले 375 किमी 50 किमी/घंटा की औसत गति से, अगले 315 किमी 70 किमी/घंटा की औसत गति से और अगले 575 किमी 57.5 किमी/घंटा की औसत गति से चलती है। पूरी यात्रा के लिए औसत गति (किमी/घंटा में) क्या है?
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Correct answer
57.5
Why this answer is correct
Given:
First distance (d1) = 375 km, Speed (s1) = 50 km/hr
Second distance (d2) = 315 km, Speed (s2) = 70 km/hr
Third distance (d3) = 575 km, Speed (s3) = 57.5 km/hr
Formula used:
Average speed = \(\dfrac{\text{Total distance}}{\text{Total time}}\)
Total distance = d1 + d2 + d3
Total time = t1 + t2 + t3, where t = \(\dfrac{\text{Distance}}{\text{Speed}}\)
Calculations:
Total distance = 375 + 315 + 575 = 1265 km
t1 = \(\dfrac{375}{50}\) = 7.5 hours
t2 = \(\dfrac{315}{70}\) = 4.5 hours
t3 = \(\dfrac{575}{57.5}\) = 10 hours
Total time = t1 + t2 + t3 = 7.5 + 4.5 + 10 = 22 hours
Average speed = \(\dfrac{1265}{22}\)
⇒ Average speed = 57.5 km/hr
∴ The correct answer is option (2).











