Multiple choice

A man can reach a certain place in $30$ hours. If he reduces his speed by $\displaystyle \dfrac {1}{15}$th, he goes $10$ km less in that time. Find his speed in km/ hr?

  1. $9$ km/hr
  2. $2$ km/hr
  3. $7$ km/hr
  4. $5$ km/hr
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let speed be v. Time = 30. Distance = 30v. New speed = v - v/15 = 14v/15. New distance = 30 * (14v/15) = 28v. Difference = 30v - 28v = 2v = 10. v = 5 km/hr.

AI explanation

If his speed reduces by 1/15th, the distance he travels in the same 30 hours also reduces by 1/15th, which is given as 10 km. By the direct proportion method, if 1/15th of the original distance is 10 km, the total original distance he covers in 30 hours is 15 times 10, or 150 km. His original speed is the total distance divided by the total time, so 150 km divided by 30 hours equals 5 km/hr. The result is 5 km/hr.