Adding 1 to large numbers like 10,000,000 is easy but subtracting 1 from 10,000,000 could be confusing. By remembering the pattern that we saw in the largest n-digit numbers and the respective (n+1)-digit numbers, you can easily not make mistakes there.
The pattern that we had before was as follows:
- 9 + 1 = 10 (largest one-digit number + 1 = smallest two-digit number)
- 99 + 1 = 100 (largest two-digit number + 1 = smallest three-digit number)
- 999 + 1 = 1000 (largest three-digit number + 1 = smallest four-digit number)
- So you can say, largest n-digit number + 1 = smallest (n+1)-digit number.
Based on this pattern you can also subtract 1 from the “smallest (n+1)-digit number to get the largest n-digit number using simple algebra. So you can also say,
Smallest (n+1)-digit number – 1 = largest n-digit number
As an example, what is 10,000,000 – 1? Since 10,000,000 is the smallest eight-digit number and you’re subtracting 1 from it, you are going to get the largest (8-1)-digit number, i.e., the the largest seven-digit number which would be 9,999,999.
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