A man standing on the bank of a river observes that the angle subtended by a tree standing on the opposite bank is 60° on his side of Bank. When he moved away 24 m from the bank, he finds the angle to be 30°. Find the breadth of the river:

12

Assume breadth of the river be x

h/x = tan 60

h = x tan 60

Also, h/(x+24) = tan 30

x tan60/(x+24) = 1/√3

x √3 / (x+24) = 1/√3

x+24 = 3x

2x = 24

x = 12 

The correct answer is Option (1) → 12