Answer:
- 1,000 m (rounded to one significant figure)
Step-by-step explanation:
The equation is:

- speed = 340m/s
- time = 6 seconds (the sound travels the distance back and forth)

Hence, the distance between the ship and the cliff is half the distance traveled by the sound:
If you round to one significant figure, because the time has just one significant figure, the answer is 1,000m.