Blonde jokes-University Final Exam

The blonde reported for her University final examination which consists of "yes/no" type questions. She took her seat in the examination hall, stares at the question paper for five minutes, and then in a fit of inspiration took her purse out, removed a coin and started tossing the coin and marking the answer sheet - Yes for Heads and No for Tails.
Within half an hour she is all done whereas the rest of the class was sweating it out.
During the last few minutes, she was seen desperately throwing the coin, swearing and sweating.
The moderator, alarmed, approached her and asked what was going on.
"I finished the exam in half an hour. But," she said, "I am rechecking my answers!!!"