One day, a class teacher was told that the school superintendent will be visiting her class on the next day. The superintendent can ask questions from anywhere and it can be easy as well as difficult. The teacher will have the liberty to choose any pupil for answering the question.
Now she is determined that the impression that is cast upon the superintendent after the inspection should be great. How will she instruct the students so that she maximizes the chances of receiving a correct answer for each question? Also, she must create the best impression. How will she do it?
It is quite simple a task. The teacher asked all her students to raise their hands on every question. However, those students who knew the right answer were asked to raise their left hand and those who did not know were asked to raise their right hand. In this manner, she would know who knows the correct answer and will pick the students accordingly. Also, since everybody will raise their hands, the final impression will be great.