Question 152148
We have 9 layers to cover. 
Each layer is round, with a diameter of 8 inches. So each layer has a radius of 4 inches

The area of a circle is given by {{{A = pi*r^2}}}
{{{A = 3.14 * 4^2}}}
{{{A = 3.14 * 16}}}
{{{A = 50.24 }}} square inches

We have 9 layers, each with an area of 50.24. So we have {{{9*50.24}}} square inches to cover. 
{{{A = 9*50.24}}} = {{{452.16}}} 

One batch of cream covers 54 square inches.
{{{BatchesRequired = 452.16/54}}}
{{{BatchesRequired = 8.37}}}

Assuming Marcus won't or can't make less than a full batch, he'll need 9 batches to cover the entire cake. 

If he has a little brother or sister, there will be lots of cream left over. Lot's of opportunity for them to 'lick the spoon'