A speaks truth in 75% of cases and B in 80% of cases. In what percent of cases are they likely to contradict each other in narrating the same event?

Answer: Option A

Different possible cases of contradiction,
A speaks truth and B does not speaks truth.
Or, A does not speak truth and B speaks truth.
$$\begin{array}{rl}& =\left(\frac{3}{4}\times \frac{1}{5}\right)+\left(\frac{1}{4}\times \frac{4}{5}\right)\\ & =\frac{3}{20}+\frac{4}{20}\\ & =\frac{7}{20}\\ & =35\%\end{array}$$