A 5 m pole long ladder is placed leaning forward on a vertical wall , such that it reaches the wall at a point 4 m high. If the foot of the ladder is moved 1.6 m toward the wall then find the distance by which the top of the ladder slide upwards on the wall.

 

Initially AD is the ladder of length 5 m which reaches the wall at the point D which is 4 m high from C. 

When we move it 1.6m towards the wall, now it's at point B in the figure. The topp of the ladder now reaches point E on wall. 

We have to find the distance DE. In the figure, DE=x m and BC=y m. AD=BE=5 m (length of the ladder)

In the right angled triangle ACD, we have

Similarly, in the right angled triangle BCE, we have

Hence, the top of the ladder slides upward by a distance of 0.8 m.