MCQ
The probability that a randomly chosen one-one function from the set $\{a, b, c, d\}$ to the set $\{1,2,3,4,5\}$ satisfies $f(a)+2 f(b)-f(c)=f(d)$ is
  • A
    $\frac{1}{24}$
  • B
    $\frac{1}{40}$
  • C
    $\frac{1}{30}$
  • $\frac{1}{20}$

Answer

Correct option: D.
$\frac{1}{20}$
d
$n ( s )=5_{ c _{4}} \times 4 !=120$ 

$f ( a )$       + $2 f(b)$        = $f ( c )$       + $f ( d )$
$5$ $2 \times 1$ $4$ $4$
$4$ $2 \times 2$ $3$ $5$
$1$ $2 \times 3$ $2$ $5$

$n ( A )=2 \times 3=6$

$\therefore P ( A )=\frac{ n ( A )}{ n ( s )}=\frac{6}{120}=\frac{1}{20}$

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