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Rounding


Rounding is the process of reducing the number of significant digits in a number. The result of rounding is a "shorter" number having fewer non-zero digits yet similar in magnitude. The result is less precise but easier to use.

For example: 53 rounded to the nearest tenth is 50, because 53 is closer to 50 than to 60.

Methodology

  • Decide which is the last digit (e.g., tenths, hundredths) to keep
  • Increase it by 1 if the next digit is 5 or more (known as rounding up)
  • Leave it the same if the next digit is 4 or less (known as rounding down)
Examples:
  • 81.042 rounded to hundredths is 81.04 (because the next digit, 2, is less than 5)
  • 363.045 rounded to hundredths is 363.05 (because the next digit, 5, is 5 or more)
  • 2.0437 rounded to hundredths is 2.04 (because the next digit, 3, is less than 5)

For negative numbers the absolute value is rounded.

Examples:

  • −31.1349 rounded to hundredths is −31.13
  • −5.1350 rounded to hundredths is −5.14