First we find the measurement of dark dot .
ANd for that we have to use the formula of the angle formed by the intersection of chord .
Let the dark dot be t.
So we have

t and z are linear pair and sum of angles of linear pair =180 degree.
So we get

Answer:
4800m
Step-by-step explanation:
"correct to the nearest 10 meters" means that the height can vary ± 10 meters.
4810 m ± 10 m = 4800 to 4820
4800 is the least possible height.
Since the probability of the coin landing leads is 1/2, simply cube 1/2 to arrive at your answer: 1/8.
You cube 1/2 because you must land heads three times in a row and each flip is independent from other flips.