An aeroplane flying horizontally at a height of 2500m above the ground is observed at an elevation of 60°.After 15 seconds, the elevation is observed to be 30°.Find the speed of the aeroplane in km per hour?
A ladder leans against a wall making an angle of 45° with the ground.It reaches(√3-√2)m higher when the angle with the ground is made 60°.How long is the ladder?