Movement in rear wheel, sideways, not fowards and backwards

G'day guys and gals,
Just a quick couple of questions: Have any of you ever had to replace the rear wheel bearings?? I noticed a small amount of sideways movement in the rear wheel last week and after clocking up some 1700km over the easter long weekend, that small movement has become a large movement!! I have heard that there are 2 or 3 bearings in the rear wheel, does anyone know how many there actually are and how much they each normally cost??
Cheers

 

cheers

thanks for that mate, you were right, except i only had to pay $25 each for the 2 bearings in the rear wheel and we now have zero movement!!