A speaks truth in 60% of the cases, while B in 90% of the cases. In what percent of cases are they likely to contradict each other in stating the same fact? In the cases of contradiction do you think, the statement of B will carry more weight as he speaks truth in more number of cases than A?
Let the probability that A and B speak truth be P(A) and P(B) respectively.
Therefore, 
A and B can contradict in stating a fact when one is speaking the truth and other is not speaking the truth.
Case 1: A is speaking the truth and B is not speaking the truth.
Case 2: A is not speaking the truth and B is speaking the truth.
Required Probability = 
Percentage of cases in which they are likely to contradict in stating the same fact =
From case 1, it is clear that is not necessary that the statement of B will carry more weight as he speaks truth in more number of cases than A.
