1.

Let A be the set of 4-digit numbers `a_1 a_2 a_3 a_4` where `a_1 > a_2 > a_3 > a_4`, then `n(A)` is equal toA. 126B. 84C. 210D. None of these

Answer» Correct Answer - C
Any selection of four digits from the ten digits 0,1,2,3,. . . ,9 gives one number.
So, the required number of numbers`=^(10)C_(4)=120`


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