Multiple choice

A man travels A to B distance at a speed of 12 km/hr and returns at a speed of 9 km/hr. If the total time taken by him is 2 hr 20 min, the A to B distance is

  1. 35 km

  2. 21 km

  3. 9 km

  4. 12 km
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let distance be D. Time = D/12 + D/9 = 2 hours 20 minutes = 7/3 hours. (3D + 4D) / 36 = 7/3. 7D / 36 = 7/3. D = 36/3 = 12 km.

AI explanation

Let the one-way distance between A and B be D kilometers, and convert the total travel time of 2 hours 20 minutes into a single fraction, which is 7/3 hours. Using the fundamental identity time equals distance divided by speed, the equation for the round trip is D divided by 12 plus D divided by 9 equals 7/3. Adding the fractions on the left gives 3D plus 4D divided by 36, which equals 7D divided by 36, so 7D/36 = 7/3. Solving this linear equation yields D equals 12, meaning the distance from A to B is 12 km.

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