OnMobile Written test puzzle -2

Three masters of logic wanted to find out who was the wisest one. So they invited the grand master, who took them into a dark room and said: "I will paint each one of you a red or a blue dot on your forehead. When you walk out and you see at least one red point, raise your hands. The one who says what colour is the dot on his own forehead first, wins." Then he painted only red dots on every one. When they went out everybody had their hands up and after a while one of them said: "I have a red dot on my head."
How could he be so sure?


  1. lets suppose the 3 persons are A, B and C and let A answers finally. As B & C hv raised their hands, so A knows that B and C hv seen a red dot. Now , it may b that they hv seen the red dot on each other's head. so, he is confused initially. But after a while, he notices that had there been a blue dot on his head, one of the other two must hv known about the colour of the dot on their head. But as they hv not replied yet so I hv a red dot on my head.


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