Multiple choice

A boat takes 5 hours to go 20 km against the river current. If the speed of the river-current is 3 km/hr, the speed of the boat in still water is :

  1. 10 km/hr

  2. 6 km/hr

  3. 7 km/hr

  4. 5 km/hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The boat's effective speed against the current is 20 km / 5 hours = 4 km/hr. Against the current, effective speed equals boat speed minus current speed. Therefore, boat speed in still water = 4 + 3 = 7 km/hr.

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