# Mind Teasers – Set 1

## 1. Students in Class

A problem has been proposed in class. At the end of the lesson it turned out that the number of boys, who had solved the problem, was the same as the number of girls, who had not solved it. Were there more girls in the class than students who had solved the problem?

## 2. Are you a liar?

Robinson found himself on an island where some of the people were liars, and others always told the truth. When he met with one of the inhabitant of the island, he asked him: “Are you a liar or not?” “I’m not a liar”, answered the person. “All right, if it is so, you’ll be my companion”, Robinson said. After a while they saw another man. Robinson pointed to the man and asked his new friend, “Could you, please, ask him, if he is a liar or not?” The new friend asked the question to the man, came back and said, “He said he was not a liar”. “All right, now I’m convinced that you are not a liar!” smiled Robinson. What convinced Robinson?

## 3. Defective Box

10 cigarette boxes each having 10 cigarettes are placed on a table. Each cigarette weighs 10 gram in a normal box but one defective box has each cigarette weighing 9 grams in it. You are allowed to use a “weighing machine” only once and tell which box is defective.

### One Thought on “Mind Teasers – Set 1”

1. Shashank on December 6, 2015 at 1:15 pm said:

The Defective box problem can be done in one another way. Put all the boxes together & then gradually pick each box. The box which will show a decreased weight of 90 will be defective.