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14.Probability
medium
Let $S=\{1,2,3,4,5,6\} .$ Then the probability that a randomly chosen onto function $\mathrm{g}$ from $\mathrm{S}$ to $\mathrm{S}$ satisfies $g(3)=2 g(1)$ is :
A
$\frac{1}{10}$
B
$\frac{1}{15}$
C
$\frac{1}{5}$
D
$\frac{1}{30}$
(JEE MAIN-2021)
Solution
$\mathrm{g}(3)=2 \mathrm{~g}(1)$ can be defined in $3$ ways
number of onto functions in this condition $=3 \times 4 !$
Total number of onto functions $=6 !$
Required probability $=\frac{3 \times 4 !}{6 !}=\frac{1}{10}$
Standard 11
Mathematics