I got 20.
As the radius = 2 => Diameter = 4. So, we can think of the cylinders as boxes with dimension 4*4*12. So, on the surface area of 20*16, we can keep (20/4)*(16/4) = 20 cylinders. Cann't fit anything in rest of the volume left ((14-12)*16*20). So, final answer = 20.
Can anyone think of any easier way of doing it?
ruhi160184 - simply dividing the volumes may not work due to the shape of cyliner. When fit in a box some space will remain between 4 cyliners that cann't be filled.