CBSE Class 12-science Answered

(b) 35%

The probability that A will state the fact truthfully is 75% and falsely is 25%.

and for B, it is, 80% and 20% respectively.

Contradiction of their statements will occur if,

 A tells truth AND B tell false OR B tells truth AND A tells false.

 A tells truth AND B tell false =(0.75)(0.20) 

 A tells truth AND B tell false =(0.8)(0.25) 

Therefore the probability of A and B contradicting the same statement is, (0.75)(0.20) + (0.8)(0.25) = 0.35 i.e. 35%.

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