The angle of elevation of a jet fighter from a point $P$ on the ground is ${60}^o$. After $5 s$ of flight, the angle of elevation changes to ${45}^o$. If the jet is flying at a height of $3000 m$, then the speed of the jet (in $m/s$) is

A ladder $10 m$ long is leaning against a vertical wall. It makes an angle of $60°$ with the ground. How far is the foot of the ladder from the wall?

X is $5 m$ tall and he notices that he casts a shadow that is $3 m$ long. He then measures that the shadow cast by his school building is $30 m$ long. How tall is the building?

Two poles of the height $12 m$ and $17 m$ stand vertically upright on a plain ground. If the distance between their feet is $12 m$, find the distance between their tops.