JEE MAIN - Mathematics (2022 - 29th July Morning Shift - No. 15)
Let $$S=\{1,2,3, \ldots, 2022\}$$. Then the probability, that a randomly chosen number n from the set S such that $$\mathrm{HCF}\,(\mathrm{n}, 2022)=1$$, is :
$$\frac{128}{1011}$$
$$\frac{166}{1011}$$
$$\frac{127}{337}$$
$$\frac{112}{337}$$
Explanation
S = {1, 2, 3, .......... 2022}
HCF (n, 2022) = 1
$$\Rightarrow$$ n and 2022 have no common factor
Total elements = 2022
2022 = 2 $$\times$$ 3 $$\times$$ 337
M : numbers divisible by 2.
{2, 4, 6, ........, 2022}$$\,\,\,\,$$ n(M) = 1011
N : numbers divisible by 3.
{3, 6, 9, ........, 2022}$$\,\,\,\,$$ n(N) = 674
L : numbers divisible by 6.
{6, 12, 18, ........, 2022}$$\,\,\,\,$$ n(L) = 337
n(M $$\cup$$ N) = n(M) + n(N) $$-$$ n(L)
= 1011 + 674 $$-$$ 337
= 1348
0 = Number divisible by 337 but not in M $$\cup$$ N
{337, 1685}
Number divisible by 2, 3 or 337
= 1348 + 2 = 1350
Required probability $$ = {{2022 - 1350} \over {2022}}$$
$$ = {{672} \over {2022}}$$
$$ = {{112} \over {337}}$$
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