Mind reader-part-2.(read carefully)
There is a magician who can read minds.
He asks a person to think of a random natural number.
There is a box in which he puts his prediction.
He has 30 assistants out of which 7 can read minds perfectly and 8 can do it such that the sum of all their numbers is equal to the prediction. The remaining assistants are beginners and just guess such that out of the remaining 15 people, only one guesses correctly and one of them doesn't predict at all.
All the predictions are fully mixed up and a random person picks up a prediction.
Considering that the person cant change his mind and the magician and his assistants are highly logical, what is the probability that the prediction is true?
Note:- the predictions cant be negative numbers.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
First there is no relevance with the number.
There are 31 predictions in total but one of them doesn't predict.
So, number of prediction is 30.
The number of sure predictions are 1(magician) + 7(perfect assistants) + 1(*) + 1(beginner assistants) = 10.
Let us take the case of the 8 people whose sum of predictions is equal to the number.
In this case the maximum number of correct prediction is 1.
Because, the only way a person in that 8 people can guess right is that he selects the number and all others select 0(it is not negative).
Since the assistants are highly logical, they would prefer to get more probability and they will follow the above solution.
That means that the probability is 33%.