Which of the following statement is correct? I. If downstream and upstream of…
2021
Which of the following statement is correct? I. If downstream and upstream of a boat are 12 km/hr and 6 km/hr respectively, then what is the speed of boat in still water is 9 km/hr. II. Length of train is 1200 meters. If it can cross a stationary pole in 10 seconds, the speed of train is 43.2 km/hr.
- A.
Only I
- B.
Only II
- C.
Both I and II
- D.
Neither I nor II
Attempted by 21 students.
Show answer & explanation
Correct answer: A
Statement I: still-water speed = (downstream + upstream) / 2 = (12 + 6) / 2 = 9 km/hr, so it is correct.
Statement II: 1200 m in 10 seconds means 120 m/s = 432 km/hr, not 43.2 km/hr, so it is incorrect.
Therefore, only statement I is correct.