Multiple choice

A man covered a distance of $2000$ km in $18$ hours partly by bus at $72$ km/hr and partly by train at $160$ km/hr. The distance covered by bus is

  1. $860$ km
  2. $640$ km
  3. $1280$ km
  4. $720$ km
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let distance by bus be d. Time = d/72 + (2000-d)/160 = 18. Multiply by 720: 10d + 4.5(2000-d) = 12960. 10d + 9000 - 4.5d = 12960. 5.5d = 3960. d = 720.

AI explanation

Let the distance covered by bus be x kilometers, meaning the distance covered by train is (2000 - x) kilometers. Using the formula time equals distance divided by speed, the total time is x divided by 72 plus (2000 - x) divided by 160, which equals 18 hours. Multiplying the entire equation by 1440 gives 20x plus 18000 minus 9x equals 25920, which simplifies to 11x equals 7920. Therefore, the distance covered by the bus is 720 km.

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