How should I use "If Cases" in English grammar?

Answer 1

You can use "If" cases to express possibilities. So for an example, let's say you go to the store and you need Apples. Apples cost $4 each and you need 5 apples. You want to know how much money to bring so you can buy the apples. So you would say,

If I buy 5 apples I will need to bring $20

You are saying If because there is you are going to buy apples and there is a possibility that they will cost $20 all together.