Question

Man on cliff observes a boat at angle of depression of 30 which is approaching the shore at uniform speed. 6 minutes later, the angle of depression of boat is 60. Find time taken by boat to reach shore?

Answer 1

Explanation:

Let the speed be x km/h

Let the time be t

In △ADC,

tan30°=

h

xt

​

3

​

1

​

=

h

xt

​

h= xt

In △ABD,

tan60°=

h

x(6+t)

h=

x(t+6)

3​

xt=

x(t+6)

3t=6+t

t=3 seconds

∴ total time taken=6+3=9 seconds