Question

A $15$ m long ladder rests against a vertical wall and reaches to a window. If the window is $12$ m above the ground, how far is the foot of the ladder from the wall(in m)?

Answer 1

Consider the ladder wall system as a right angled triangle such that length of the ladder be the hypotenuse, length of wall till the ladder be perpendicular and distance between the foot be the base
Thus, $H^2=P^2+a^2$
${15}^2={12}^2+a^2$
$225=144+a^2$
$a^2=81$
$a=9$ cm
Thus, distance between the foot of the ladder and the wall is 9 cm.