Multiple choice

A jogger covered a certain distance at some speed. Had he moved 3 km/hr faster, he would have taken 20 minutes less. If he had moved 1 km/hr slower, he would have taken 10 minutes more. What is the distance (in km) that he jogged?

  1. 9

  2. 10

  3. 12

  4. 8
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let distance be D and speed be S. D/S - D/(S+3) = 20/60 = 1/3. D/(S-1) - D/S = 10/60 = 1/6. Solving these two equations gives S = 9 km/hr and D = 12 km.

AI explanation

Let the usual speed be s km/hr and the usual time be t hours; the distance is given by s * t. The two conditions give the equations s * t = (s + 3)(t - 1/3) and s * t = (s - 1)(t + 1/6), which expand to s = 3t - 1 and s = t + 1. Solving these equations yields t = 1 hour and s = 6 km/hr. Therefore, the distance jogged is 6 * 1 = 12 km.

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