Multiple Variables in a single column

What I would like to do is to set up a column where I can input a number 1 to 4 and it will assign the number a value, such as 1 = 20, 2 =25, 3 = 30, 4= 35. I would like to be able to do this all in one column. I have not used excel very long and I am having a difficult time doing this. I took basic programming so I understand some terminology with this stuff, such as if statements. I also already know how to add, multiply, subtract, and divide, if any of those functions are necessary to get the column to do this. Thank You.