Multiple choice

A car takes 7 hours to travel a certain distance. If it had increased its speed by 9 km/hr, it would have taken 4 hours to travel the distance. The distance is

  1. 72 km

  2. 120 km

  3. 84 km

  4. 640 km

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let distance be D and speed be S. D = 7S. Also, D = 4(S+9). Setting them equal: 7S = 4S + 36, so 3S = 36, S = 12 km/hr. Distance = 7 * 12 = 84 km.

AI explanation

Let the original speed of the car be v km/hr and the distance be d km. We are given d/v = 7 and d/(v + 9) = 4. Equating the distance gives 7v = 4v + 36, which means v = 12 km/hr. The distance is 7 multiplied by 12, resulting in 84 km.

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