Multiple choice

A truck covers a distance of 480 km at a certain speed. If the speed is decreased by 8 km/h, it would have taken 2 hours more to cover the same distance. 50% of its original speed (in km/h) is:

  1. 40

  2. 48

  3. 24

  4. 20
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let original speed = v km/h. Time = 480/v. New time = 480/(v-8) = 480/v + 2. So 480/(v-8) - 480/v = 2. Solving: 480[v - (v-8)]/[v(v-8)] = 2, giving 3840 = v(v-8), so v = 48. 50% of 48 = 24.

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