Multiple choice

A boat travels 48 km upstream in 12 h and 40 km downstream in 8 h. Then, the speed of a boat in still water and the speed of current are respectively.

  1. $3.5, 1.5$
  2. $4, 1$
  3. $4.5, 0.5$
  4. $2.5, 2.5$
  5. $None of these$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Upstream speed = boat - current = 48/12 = 4 km/h. Downstream speed = boat + current = 40/8 = 5 km/h. Adding: 2 × boat = 9, so boat = 4.5 km/h. Subtracting: 2 × current = 1, so current = 0.5 km/h. This uses the standard formula for relative speed in flowing water.

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