Math is used for many things, but for me I will be using it in field of culinary arts. When many people think of math they automatically think of algebra or geometry, math is those things plus much more. Fractions, Measurements and weights are the kind of math that i will be using most in cooking. Classical cooking technique, baking and catering are all greatly effected by basic math fundamentals.
I have to use exact measurements when making a beurre blanc or a consomme. measurements and math are very important to get the proper flavor and texture from any food being prepared . food is very precise, you need to use base elements before you can start improvising on your own. cooking is about more lenient in this regard but baking is a whole other world. Baking and pastry is pretty much chemistry but with food instead of raw elements. In chemistry of cooking you combine certain ingredients to produce other more finished products. When you are doing that every element needs to be weighed out exactly and combined in a certain manner, otherwise you will just end up with a mess.
Catering is another place math is used to translate regular recipes into great volume, simple addition and multiplication aid in this field. If you have a simple recipe that serves 4-6 people you need to be able to multiply that by 10 or even 15 to feed many more people. Without basic math fundamentals one would not be able to create a meal or translate a recipe for a large catering job.