Multiple choice

A train travels from one station X to another station Y at a rate of $20$ km/hr and returns at the rate of $30$ km/hr. The average speed of the total journey is

  1. $25$ km/hr
  2. $24$ km/hr
  3. $35$ km/hr
  4. $40$ km/hr
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Average speed for equal distances is 2xy / (x + y). Here, 2 * 20 * 30 / (20 + 30) = 1200 / 50 = 24 km/hr.

AI explanation

For a journey where equal distances are travelled at two different speeds, the average speed is found using the harmonic mean formula: 2xy / (x + y). Substituting the speeds of 20 km/hr and 30 km/hr gives (2 * 20 * 30) / (20 + 30). This simplifies to 1200 / 50, which equals 24 km/hr.

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