Multiple choice

In covering a distance of 30 km, A takes 2 hours more than B. If A doubles his speed, then he would take 1 hour less than B. A's speed (in km/hr.) is

  1. 5

  2. 6

  3. 6.25

  4. 7.5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let A's speed = a km/hr, B's speed = b km/hr. A takes 2 hours more: 30/a = 30/b + 2. When A doubles speed: 30/(2a) = 30/b - 1. Solving: a = 5 km/hr, b = 6 km/hr. Check: 30/5 = 6 hrs, 30/6 = 4 hrs (difference 2 ✓). Doubled: 30/10 = 3 hrs, which is 1 less than 4 ✓. Option A is correct.

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