Is there a penalty if you check a quiz question answer and it is wrong, or can you carry on to get full marks by making enough tries until you finally get it right?  In particular, what is a typical penalty (as a %) for checking a question and getting it wrong?  Enter your answer in the box below. 

For example, if you think that there is no penalty, enter 0.  If you think that the penalty is 30% per check, enter 30. (Round your answer to 2 decimal places)