Draw a figure based on given instructions.
Let O be the point of the observer and OB = Length of the string from the level of ground.
AB = 75 m and ∠OAB = 90° and ∠AOB = 60°.
Let OB = x
From the right ∆OAB, we have
cosec 60° = OB/AB
2/√3 = x/75
x = 50√3 = 86.6
Length of the string is 86.6 m.