Sentence examples for add one from inspiring English sources

The phrase "add one" is correct and can be used in written English.
It is often used in instructions or mathematical equations to indicate the action of increasing a number by one. Example: To complete the sequence, add one to each number: 1, 2, 3, 4, __. (The answer would be 5.) Alternatively, you can also use "increase by one" or "plus one" in place of "add one." Example: Please add one tablespoon of salt to the mixture.