2 tier cake - quantities for a novice

[FusionChefGeoff]

So I'm attempting DS birthday cake - baking today, freezing, then icing with ready roll day before the party.

I've got 2 x shallow 7" tins (for 1 sandwiched layer) and 1x deep 6" tin (to cut in 1/2 then sandwich for top layer). I'd like both layers to be roughly the same height.

I've tried to dust off my maths A level to work out what proportion of mixture I need in each tin and I've failed miserably.

So:
A) what quantity mix should I make (16, 16, 16, 8?)
B) what proportion should be in each tin?

Extra marks for showing your workings out

Why don't you just use the same tin twice

I would put half the mix in the 6" and a quarter in each of the 7".

Chances are the 6" will end up a bit more dome-like and will need the top to be evened off. With the flatter 7"s you can even them with buttercream layers of needed.

But, a 6" and 7" layered cake will basically look like they are the same size, it only allows half an inch edge the whole way around. Even if you are offsetting and having the cake set back into the corner it's still not much of a ledge.

You're better off having 8 and 6" if possible.