A man on the top of a tower, standing on the sea-shore, finds that a boat coming towards him takes 10 minutes for the angle of depression to change from 30º to 60º. How soon the boat reach the sea-shore ?
Show answer & explanation
Correct answer: A
Explanation
The correct option is 1.
height of tower = h
tan 30° = 
tan 60° = 
= x
h√3 = x + y
h√3 = + y
= y
y = 2x
time taken to travel y distance = 10mins
time taken to travel x distance ( half of y distance) = 5 mins