2017 · Q45
A man rows down a river 18 km in 4 hours with the stream and returns in 10 hours. Consider the following statements :
- 1The speed of the man against the stream is 1.8 km/hr.
- 2The speed of the man in still water is 3.15 km/hr.
- 3The speed of the stream is 1.35 km/hr.
Which of the above statements are correct ?
Elementary MathematicsTime, Speed and Distance
- A1 and 2 only
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Explanation
Downstream speed = 18/4 = 4.5 km/h; upstream speed = 18/10 = 1.8 km/h. Statement 1 (speed against the stream is 1.8) is true. Still-water speed = (4.5+1.8)/2 = 3.15, so statement 2 is true. Stream speed = (4.5−1.8)/2 = 1.35, so statement 3 is true. All three are correct. Hence option (D) 1, 2 and 3.