Adding and Subtracting One to Large Numbers

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.
These articles are used by the author in a series of mathematics courses that will teach you mathematics from the sixth standard all the way up to 12th standard.

The purpose of these courses are to help us understand mathematics so that you can use them professionally well. There is a road map that we have put together about the all the courses included, where to starts, etc. To know more about that and have access to those courses, please visit mathematics page on Great IT Courses. Thank you.

Author: John Raschedian

Web Developer

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