Understanding place value and the structure of numbers is a fundamental part of primary school mathematics. A common question asked in exams is identifying the biggest (or largest) 4-digit number.
Largest 1-digit number: 9
Largest 2-digit number: 99
Largest 3-digit number: 999
The biggest 4-digit number is 9999 (Nine thousand nine hundred ninety-nine).
Why? Because 9 is the highest single digit in the decimal system. To create the largest possible number for any given amount of digits, you simply fill every place value with a 9.
If you add exactly 1 to the biggest 4-digit number (9999 + 1), you get 10,000. 10,000 is the smallest 5-digit number.
Conversely, the smallest possible 4-digit number is 1000 (One thousand). If you subtract 1 from 1000 (1000 - 1), you drop down to 999, which is the biggest 3-digit number.
The biggest 4-digit number is 9999, but that is an odd number. The biggest 4-digit even number is 9998.
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