Two fair dice, each with faces numbered 1 , 2 , 3 , 4 , 5 and 6 , are rolled together and the sum of the…

Two fair dice, each with faces numbered 1,2,3,4,5 and 6, are rolled together and the sum of the numbers on the faces is observed. This process is repeated till the sum is either a prime number or a perfect square. Suppose the sum turns out to be a perfect square before it turns out to be a prime number. If p is the probability that this perfect square is an odd number, then the value of 14p is_____

Solution

Perfect Square can be 4 or 9, which can be obtained by 1,3,3,1,2,2,6,33,6,5,4,4,5.

Prime Number can be 2 or 3 or 5 or 7 or 11, which can be obtained by 

1,1,1,2,2,1,1,4,4,1,2,3,3,2,1,6,6,1,5,2,2,5,3,4,4,3,6,5,5,6

P(square or prime)=2236

P Perfect square is odd  perfect square before prime =436+1436.436+1436.1436.436+....736+1436.736+1436.1436.736+......

=4361-14367361-1436=47=P

14 P=8

Asked in: JEE Advanced 2020 (Paper 2)

Practice more Probability questions on Aicharya