Multiple choice

DIRECTION for the question: Solve the following question and mark the best possible option. A motorist covers a distance of 39 km in 45 minutes by moving at a speed of x kmph for the first 15 minutes, then moving at a double the speed for the next 20 minutes and then again moving at his original speed for the rest of the journey. Then, x is equal to :

  1. 36

  2. 22

  3. 25

  4. 340

  5. 30
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total distance = 39 km. Time = 45 min = 0.75 hours. Let speed be x. 15 min = 0.25 h, 20 min = 1/3 h, 10 min = 1/6 h. Distance = (x * 0.25) + (2x * 1/3) + (x * 1/6) = 39. (1/4 + 2/3 + 1/6)x = 39. (3/12 + 8/12 + 2/12)x = 39. (13/12)x = 39. x = 39 * 12 / 13 = 3 * 12 = 36 kmph.

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