Loading [MathJax]/jax/output/HTML-CSS/jax.js


1)

 If the angles of elevation of the top of a tower from three  collinear points A, B and C on a line leading  to the foot of the tower are 30° , 45° and 60° respectively , then the ratio AB:BC is


A) 3:1

B) 3:2

C) 1:3

D) 2:3

Answer:

Option A

Explanation:

 According to the given information.

the figure should be as follows.

  Let the height of tower =h

432021637_mm.JPG

 In   EDA,

    tan300=EDAD

  13=EDAD=hAD

                    AD=h3

 In  EDB,

                        tan450=hBDBD=h

 EDC

                 tan600=hCDCD=h3

 Now,        ABBC=ADBDBDCD

        ABBC=h3hhh3

         ABBC=h(31)h(31)3

                  ABBC=(31)(31)×3

                  ABBC=31

    AB:BC=   3:1