So, here's what we have got.
The coins are cylindrical, so for the coins....
thickness is height here, so h₁=0.2 cm
Then for the cylinder..
so, we have got everything in cms, then all that is remained to do is to compare both ones.
so, both are cylinders.
Here the 'n' is the no. of the coins.
so, we've got
(225)² (10) = (n) (0.75)² (0.2)
506250=(n) (0.5625) (0.2)
[note: I think there may be a mistake because I'm not sure if the diameter of the main cylinder is 4.5 meters, I'd like to tell you to check out if that value is 4.5 cms.]
Hope it helped. ^_^