RRB NTPC CBT 2 Level 6 Exam 9 May 2022 Shift 2

A man on a cliff observes a boat at an angle of depression of 30°, which is approaching the shore to a point exactly beneath the observer, at a uniform speed. Ten minutes later, the angle of depression of the boat is found to be 60°. Find the total time taken by the boat to reach the shore.