Multiple choice

Directions: The following question consists of three statements A, B and C. You have to determine which of the statements is/are necessary to answer the question. In a military convoy, if truck A followed truck B through a road tunnel that is 1 km long, how many seconds did it take truck A to cross the tunnel? A. Truck A drove into the tunnel exactly 3 seconds after truck B drove into it. B. Truck A drove out exactly 2 seconds after truck B drove out. C. Truck B travelled through the tunnel at a constant speed of 60 km/hr.

  1. Any 2 of them

  2. A and B both

  3. A and B or C

  4. All statements are required.

  5. All even together are not sufficient.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

To find the time it takes for truck A to cross the tunnel, we need the speed of truck A and the length of the tunnel. Statement C gives the speed of truck B, and statements A and B provide the relative timing of entry and exit, which allows us to calculate the speed of truck A relative to truck B. All three pieces of information are necessary to determine the specific duration.

AI explanation

Statement A establishes the time gap between the trucks entering the tunnel, and statement B establishes the time gap between them exiting. Because truck A entered 3 seconds after truck B but exited only 2 seconds after, truck A gained 1 second on truck B, meaning it took truck A 1 second less to travel the 1 km tunnel. However, to find the exact time truck A spent in the tunnel, you must know the actual time truck B spent, which requires using its speed of 60 km/hr from statement C. Truck B travels 1 km at 60 km/hr in 60 seconds, so truck A took 59 seconds; consequently, all three statements are required.

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