I am not particularly good at maths. It took me three attempts to pass my 'O' level. Which makes it rather ironic that I spent a good part of my career working in banking.

Anyway, I don't believe I'm alone in this but there are few mathematical subjects that are actually relevant in everyday life. I've never needed to use trigonometry, for example, and what on earth were matrices all about? Even mathematicians can't really tell me that, by the way.

Algebra, on the other hand, rather scarily, does have a place in the life of a mum... it's the only way to work out the ingredients required for birthday cakes.

I first discovered this during the run-up to Rhiannon's first birthday. I needed to work out the ingredients for a rather elaborate caterpillar cake made from Swiss Rolls. The maths took me all morning, but it was successful. And I was ridiculously pleased with my problem solving skill dredged up from mental filing cabinets last investigated decades ago.

Almost a decade has passed since my first foray into bakery maths and the time has come around again. Rhiannon's 10th birthday is tomorrow and I needed to make cakes to send into school and a birthday cake for, well because you have to, really.

Don't get me wrong, I like baking. As a child I spent every Saturday baking - bread, cakes, biscuits etc. In later years, this has dropped off as nobody seems to eat cake much now. Birthdays are different though. I'm not brilliant at decorating the cake, but it's fun.

Bakery maths involves a pen and paper (I can never find a calculator), a ruler (to measure the tins) and the recipe (a standard sponge cake). Then find out which size round tin the recipe applies to and extrapolate that to the non-standard tin. Easy! Hah!!

The school cakes are a traybake (chocolate dominoes) and the main birthday cake is a giant cupcake for which I'd bought a tin some time back.

So I needed to know the area of a circle, the area of a rectangle and and and... argh!

After much brainwork, I worked out that I'd need 11 eggs (!) and bake three cakes.

I've used four packs of butter, two boxes of icing sugar and, of course, the 11 eggs. And the main cake isn't yet iced; that's a job for tomorrow. I'm exhausted!

If it turns out OK, I'll post a picture of the birthday cake.

For now, here's one I made earlier... as in about three years ago.