Multiple choice

A man jogs along a certain route to a place and walks back from that place to the starting point, following the same route. What is his average speed for the entire activity? Statements: A. His jogging speed is one-and-a-half times his walking speed. B. By walking, he covers a distance of 8 km in 120 min. C. Total distance travelled by him in entire activity is 20 km.

  1. Only A and B together are sufficient.

  2. Only A and C together are sufficient.

  3. Only B and C together are sufficient.

  4. Any two of them together are sufficient.

  5. All three statements are necessary.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Average speed = Total distance / Total time. Statement A gives the ratio of speeds. Statement B gives the walking speed (8km / 2hr = 4km/h). Statement C gives the total distance. To find the average speed, we need the total time, which requires both the walking speed (from B) and the jogging speed (from A). C is redundant if we know the distance is covered in a specific route.

AI explanation

Average speed for equal distances is calculated by the formula 2uv divided by (u + v). Statement A establishes the ratio between the jogging speed and walking speed, allowing the average speed to be expressed as a single variable, such as 5w/4. Statement B provides the walking speed as 8 km divided by 2 hours, which equals 4 km/hr. Substituting this into the formula gives an exact average speed of 5 km/hr, making only A and B together sufficient. The result is Only A and B together are sufficient.

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