Explanation:
Louise calculated the height of a cylinder that has a volume of 486 pi cubic centimetres and a radius of 9 centimetres. 
The formula for the volume of cylinder is :
V = B × h
B is area of base of cylinder

i.e.

Substituting given values,

 will cancel out from both sides.
 

She forgets to cancel down 
 from both sides. So, she get height as 
. So, in the 
 should have canceled, making the correct answer 6 cm.