Question:
How many numbers with two or more digits can be formed with the digits 1,2,3,4,5,6,7,8,9, so that in every such number, each digit is used at most once and the digits appear in the ascending order?
How many numbers with two or more digits can be formed with the digits 1,2,3,4,5,6,7,8,9, so that in every such number, each digit is used at most once and the digits appear in the ascending order?
Updated On: Sep 30, 2024
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Correct Answer: 502
Solution and Explanation
As the digits appear in ascending order in the numbers, number of ways of forming a n-digit number using the 9 digits = 9Cn
Number of possible two-digit numbers which can be formed = 9C2 + 9C3 + 9C4 + 9C5 + 9C6 + 9C7 + 9C8 + 9C9
= 29 - (9C1 + 9C1)
= 512-(1+9) = 502
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