Question

A speaks the truth in 60% cases and B speaks the truth in 75% cases. The probability that they will contradict each other in describing a single event is

• A. 11/20
• B. 9/20
• C. 13/20
• D. 7/20

Answer 1

Answer: (B)

9/20

Answer 2

Required probability = P(1) P() + P( $\overline { \mathrm { A } }$ ) P(2)

= $\frac { 3 } { 5 } \times \frac { 1 } { 4 } + \frac { 2 } { 5 } \times \frac { 3 } { 4 } = \frac { 9 } { 20 }$