UPSC 2017 CDS I Math Paper

Here, AB is the building and CD isthe tree.Here, AB is the building and CD is the tree.
Let the height of the tree be h m.
AB = 90 m and CD = h m.
∴ BE = AB – AE = AB – CD
= (90 – h) m
In right ΔABC
tan‌45°=1=

AB

AC

⇒ AC = 90m
In right ΔBDE
tan‌30°=

1

√3

=

BE

DE

⇒

1

√3

=

90−h

90

 (DE=AC)
⇒90−h=30√3
⇒h=(90−30√3)m