Before you take action, you as supervisor should know what is meaning of Intern. Intern is a student or trainee who works, in order to gain work experience or satisfy requirements for a qualification.

Bare your mind that intern have rights to complaint to labour office if you simply fire them in organization as they are sign their acceptance letter to join your organization as Intern. To handle the intern is easy - you must have high patience as you become a role model also "teacher" for intern. They will learn our work style also behavior too since they zero knowledge and skills. Here some tips for you how to handle intern:

1. If several time he/she makes mistake, ask them what actual problem (without fear the intern). What actually they can't understand?
2. Teach them one more time but make sure they have book and pen to take notes while your teaching. That's how knowledge and skill receive by intern.
3. Give one example then ask them to follow while you looking at their job which is more satisfy and confident to make them good intern. Once is okay let them to do independently and ask them to show to you once it complete.
4. You should open up for them to ask you any question since they reporting under you.
5. Keep remember, they are zero knowledge and skills. If you can't handle intern, is better you find person who have 1-2 years experiences as they might easy to handle independently and more relevant to your requirement.

Hope above info is workable to you.

However, you can fire, with a valid reason. But I think your statement above cannot be the valid reason to terminate your intern.

You’re supervisor, you must bear the responsibility to teach the intern. Remember intern comes for learn from mistakes and gain experience. He is new and without much work experience.

The problem could be you. You should teach him first, some interns are just too shy to ask, and not sure if the info on google is correct.