Well, I don't have too much cake baking experience, but this might help a
little:

Max volume capacity of the two round pans:
2 * pi*radius squared*height = 471.23888 cubic inches

Max volume capacity of the rectangular pan:
11 * 15 * 2 = 330 cubic inches

330 / 471.23888 = 0.70
So my estimate is that you'd need 70% of the batter. I'm not sure about the
issues with overcooking the edges.

- Scott

"N." > wrote in message
om...
> These questions may seem like a no-brainer to some of you, but I'm not
> a baker by any stretch of the imagination so I need help!
>
> I have a recipe for a cake that recommends using two 10x3" round pans
> and yields 9 cups of batter. How much of this cake batter would I
> need to fill a 11x15x2" rectangular pan? I guess I would fill it up
> 1/2 way and then bake until it's set in the center and hope for the
> best? Would the edges be overbaked by the time the center was set?
> Can I prevent this from happening? Is there any way possible that I
> can still follow the recipe as is and make 2 sheet cake layers out of
> it so I can use a filling (whipped cream type of filling) and still
> have it coming out tasty (not dry, crumbly, etc)?
>
> Also, the key in the back of the cookbook says that a 10" round
> layered cake will yield 25 servings - does this sound about right? My
> daughter is having a birthday party and so I'll need at least 25
> servings for kids + adults.
>
> Thanks!
>
> N.