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

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The question below is from previous year CAT question from CAT 2018 exam comes from CAT Permutation and Combination: How many numbers with. Find out by answering this question which tests an aspirant’s Quantitative Ability Skills:

## CAT 2018 - Slot-1 - Permutation and Combination - Question-5 - How many numbers with

Q. 5: 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?

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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