How big of a cake to buy for a 15 table reception

It depends on how many tables you have, usually a 3-tier cake.

Cake is an ancient pastry, usually made by the oven, the cake is made with eggs, sugar, wheat flour as the main ingredients. Milk, juice, milk powder, spices, salad oil, water, shortening, baking powder as auxiliary ingredients. After mixing, modulation, baking to make a kind of sponge-like confectionery.

A cake is a type of pasta, usually sweet, typically made by baking. The main ingredients of a cake include flour, a sweetener (usually cane sugar).

The binder (usually eggs, vegans can substitute gluten and starch), shortening (usually butter or margarine, low-fat cakes will substitute fruit juice concentrate), liquids (milk, water, or fruit juices), flavors, and leavening agents (such as yeast or baking powder).

Origins:

These cakes are a symbol of ancient religious myths and miraculous superstitions. Early trade routes led to the importation of exotic spices from the Far East to the North, nuts, floral waters, citrus fruits, dates and figs from the Middle East, and sugar cane from the East and South.

During the Dark Ages in Europe, these exotic ingredients were only available to the monks and nobility, whose pastry creations consisted of things like honeyed gingerbread and flat, hard cookies. Slowly, as trade became more frequent, the eating habits of the West followed suit and changed radically.