CAT 2020 Number System Question (Medium)

Question

How many integers in the set 100, 101, 102, ..., 999 have at least one digit repeated?

Accepted Answer

We are asked How many 3-digit numbers from 100 to 999 have at least one repeated digit? Step 1 Total 3-digit numbers From 100 to 999 Total 999 100 1 900 Step 2 Count how many have all distinct digits - Hundreds digit 1 to 9 9 options - Tens digit 0 to 9 excluding the hundreds digit 9 options - Units

CAT 2020

Quantitative

Number System

Medium

How many integers in the set {100, 101, 102, ..., 999} have at least one digit repeated?

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