Multiple choice

A boat owner, eager to test the capabilities of his boat, sets off on a river journey. The boat travels 120 km upstream in 10 hours and covers the same distance downstream in 8 hours. On the following day, the boat departs from a point X and follows a pattern: it travels downstream for 2 hours, followed by upstream for 2 hours. This cycle is repeated for a total of 4 times. After completing these 4 cycles, what will be the boat's position relative to its starting point X?

  1. 16 km downstream of point X

  2. 24 km downstream of point X

  3. 28 km downstream of point X

  4. 38 km downstream of point X
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Upstream speed = 120/10 = 12 km/h. Downstream speed = 120/8 = 15 km/h. Boat speed = (15+12)/2 = 13.5 km/h, stream speed = (15-12)/2 = 1.5 km/h. In one cycle (2h down, 2h up): distance = (15*2) - (12*2) = 6 km downstream. Total for 4 cycles = 6 * 4 = 24 km.

AI explanation

The boat's upstream speed is 120 km divided by 10 hours, giving 12 km/hr, and its downstream speed is 120 km divided by 8 hours, giving 15 km/hr. In one cycle of 2 hours downstream and 2 hours upstream, the boat covers 30 km downstream and 24 km upstream. The net displacement for one cycle is 6 km downstream, so for 4 identical cycles the total displacement is 24 km downstream.

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