Multiple choice

Points A and B are 100 km apart. A car starts from point A and another from point B at the same time. If they travel towards each other, they meet after one hour; but if they travel in the same direction (of the slower one), they meet after five hours. What is the difference in their speeds?

  1. 10 kmph

  2. 25 kmph

  3. 40 kmph

  4. 20 kmph

  5. None of these
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D Correct answer
Explanation

Let speeds be u and v. (u+v) = 100/1 = 100. (u-v) = 100/5 = 20. Adding equations: 2u = 120, u = 60. Then v = 40. Difference = 60 - 40 = 20.

AI explanation

Let the speeds of the cars be x kmph and y kmph. Using the relative speed formula for objects moving towards each other, x plus y equals 100 divided by 1, which gives x plus y equals 100. When moving in the same direction, their relative speed is x minus y, leading to the equation x minus y equals 100 divided by 5, which simplifies to x minus y equals 20. Solving these equations shows the difference in their speeds, x minus y, is 20 kmph.

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