An electrician has to repair an electric fault on a pole of height 9m. He needs to reach a point 1m. below the top of the pole to undertake the repair work. How far from the foot of the pole should he place the ladder, if the ladder is 10m long?

Answer : 
Let he need to reach at point C 

Height of Pole BD  =  9  m  
And
CD =  1 m 
So
BC  = BD  -  CD  =   9 - 1  = 8 m
Length of ladder AC  =  10  m  
Let distance from foot of the pole and ladder's foot  AB  =  x  m

Now we apply Pythagoras theorem in triangle ABC  

AC²  = AB²  + BC²

10²    = x²  + 8² 

x²  = 100  - 64 

x²  = 36 

x =  6 

So,

He should place his ladder  =   6  m from the foot of the pole .                            ( Ans )