Question 152244
Remember, the area of a circle is
{{{ (pi)r^2 }}}
.
Since the cake is 8" in diameter, the radius is 4"
The area of one layer of cake is:
{{{ (pi)r^2 }}}
{{{ (3.14)4^2 }}}
{{{ (3.14)16 }}}
= 50.24 sq inches
.
Since there are eight layers:
8 * 50.24 = 401.92
.
Each recipe can cover 54 sq inches therefore,
401.92/54 = 7.44 batches
or 
8 batches (if he can't make a partial batch)