Part of the question appears to be missing.
The distance to the visible horizon varies directly with the square root of the height
of the observer above sea level. An observer 1.8 m tall can see 4.8 km out to sea when
standing on the shoreline.
I know how to do it but the answers says I'm wrong...
<--- this is meant to be proportional sign but I can't seem to find it and alpha looks close enough xD
we found k then:
but the answer is like 8. something