question_answer

A person standing on the bank of a river observes that the angle subtended by a tree on the opposite bank is \[60{}^\circ \]. When he steps back 40 metres from the bank, he finds the angle to be\[30{}^\circ \]. The breadth of the river is.

A)  20 m

B)  30 m

C)  40 m                           

D)  60 m

E)  None of these