Quantitative Aptitude – Modern Maths – Permutation and Combination – How many numbers with

Slot -1 – Quantitative Aptitude – Modern Maths – Permutation and Combination – How many numbers with two or more

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?

Answer: 510

Solution :
As all given digits are different natural numbers and we have to use them at most once, ways of arrangements for each set of digits will be exactly once.
Thus Total such numbers = 9(baseC2) + 9(baseC3) +9(baseC4) +9(baseC5) +9(baseC6) + 9(baseC7) +9(baseC8) +9(baseC9) = 2^9 – 2 = 510

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