Question

A 15 m long ladder is placed against a wall in such away that the foot of the ladder is 9 m away from the wall. Up to what height does the ladder reach the wall?
(a) 13 m
(b) 10 m
(c) 8 m
(d) 12 m

Answer 1

Suppose BC is the ladder having length 15 m is placed againts the wall OA. The foot of the ladder C is 9 m away from the foot of the wall O.

In right traingle BOC,
BC² = OC² + OB²
⇒ (15)² = (9)² + OB²
⇒ 225 = 81 + OB²
⇒ OB² = 144
⇒ OB² = (12)²
⇒ OB = 12 m
Hence, the correct answer is option (d).