Question

The probabilities of a student getting I, II and III division in an examination are respectively $\frac { 1 } { 10 } , \frac { 3 } { 5 }$and $\frac { 1 } { 4 }$. The

probability that the student fail in the examination is

• A. $\frac { 197 } { 200 }$
• B. $\frac { 27 } { 200 }$
• C. $\frac { 83 } { 100 }$
• D. None of these

Answer 1

Answer: (D)

None of these

Answer 2

A denote the event getting I;

B denote the event getting II;

C denote the event getting III; and D denote the event getting fail.

Obviously, these four events are mutually exclusive and exhaustive, therefore

$P ( A ) + P ( B ) + P ( C ) + P ( D ) = 1$ ⇒ $P ( D ) = 1 - 0.95 = 0.05$ .