Q44 / 67 · NEST (NISER) 2021 (Session 1) · Mathematics

Let $X$ be the set of all 6 -digit numbers, where all the digits of each number are from the set $\{1,2,3,4,5\}$, and any digit that appears in any one of the numbers appears at least twice (in the same number). Then the number of distinct elements in the set $X$ equals

A
1415
B
900
C
1800
Correct answer
D
1405

Hence, the correct answer is option: 'D'.

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