CAT 2023 Permutations and Combinations Question (Medium)

Question

The number of all natural numbers up to 1000 with non-repeating digits is

Accepted Answer

Step 1 We are to count how many natural numbers 1000 have all digits distinct. We consider 1-digit, 2-digit, and 3-digit numbers separately as 1000 has repeating 0s . 1-digit numbers From 1 to 9 9 numbers all distinct 2-digit numbers Tens digit 1 to 9 9 choices Units digit 0 to 9 excluding tens digi

CAT 2023

Quantitative

Permutations and Combinations

Medium

The number of all natural numbers up to 1000 with non-repeating digits is

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