Multiple choice

A boat has to travel upstream 20 km from point x of a river to point Y. The total time taken by boat in travelling from point X to Y and Y to X is 41 min 40 sec. What is the speed of boat? एक नाव को धारा के ऊर्ध्वप्रवाह नदी के बिन्दु X से बिन्दु Y तक 20 किमी. जाना है। बिन्दु X से Y तक नाव को यात्रा करने में तथा Y से X तक यात्रा करने में लिया गया कुल समय 41 मिनट 40 सेकेण्ड है। नाव की चाल क्या है?

  1. 20 km/hr./ किमी./घण्टा

  2. 24 km/hr./ किमी./घण्टा

  3. 48 km/hr./ किमी./घण्टा

  4. Can't be determined/निर्धारित नहीं किया जा सकता
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

We know the one-way distance is 20 km and total time for round trip is 41 min 40 sec = 2500 seconds. Let boat speed = b, stream speed = s. Upstream: 20/(b-s) + Downstream: 20/(b+s) = 2500/3600 hours. This is one equation with two unknowns (b and s). We cannot determine boat speed uniquely without knowing the stream speed. Options A, B, and C are specific values that can't be verified.

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