Question:

How many integers in the set {100, 101, 102, ..., 999} have at least one digit repeated?
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Updated On: Jul 8, 2024
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The Correct Option is A

Approach Solution - 1

The given set is a set of all three-digit numbers and the number of numbers in the set \(=900\).
The number of three-digit numbers having no digits repeating = \(9×9×8 = 648\)
Required answer =\(900-648=252\)

So, the correct option is (A): \(252\)

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Approach Solution -2

The total numbers of integers are = 999 - 100 + 1 = 900
Let N be the number of integers with No Repeated digits
Total 10 digits we have (0, 1 ........, 9)
The 1st digit can't be 0, as we have 9 digits
For the 2nd digit, we have 9 digits,
For the 3rd digit, we have 8 digits
So, Total number of digits with no repetition
⇒ N = 9 × 9 × 8 = 648
Integers with at least one digit repeated,
= 900 - N
= 900 - 648 = 252
Hence, There will be 252 integers with at least one digit repetition.

So, the correct option is (A): \(252\)

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