AP Police SI practice question
Meena goes from home to office at 21 km/h and returns by the same route at 28 km/h. What is the average speed for the whole journey?
From a AP Police SI Quantitative Aptitude practice set · Quantitative Aptitude
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Correct answer: (A) 24 km/h
Equal distances at speeds u and v ⇒ average speed = 2uv/(u + v) = 2 × 21 × 28/(21 + 28) = 1176/49 = 24 km/h. (The arithmetic mean 24.5 km/h is the standard trap — the slower leg takes longer, so the average is pulled below the mean.)
हिंदी में प्रश्न
मीना घर से कार्यालय 21 किमी/घंटा की चाल से जाता/जाती है और उसी मार्ग से 28 किमी/घंटा की चाल से लौटता/लौटती है। पूरी यात्रा की औसत चाल क्या है?
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सही उत्तर: (A) 24 किमी/घंटा
समान दूरियाँ u और v चाल से ⇒ औसत चाल = 2uv/(u + v) = 2 × 21 × 28/(21 + 28) = 1176/49 = 24 किमी/घंटा। (समांतर माध्य 24.5 किमी/घंटा मानक जाल है — धीमा भाग अधिक समय लेता है, इसलिए औसत माध्य से नीचे रहता है।)
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