Rounding Numbers

Rounding, significant figures, decimal places

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Exercises

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Key Skills

Rounding rules

SL Core 1.1

There are standardized rules for how to approximate numerical values:

If the digit after the one being rounded off is LESS than 5 (0,1,2,3, or 4), we round down.
If the digit after the one being rounded off is 5 OR MORE (5,6,7,8, or 9), we round up.
1.34∣5→1.35
1.34∣4→1.34

Significant figures

SL Core 1.1

A significant figure is any digit that is not a leading or trailing zero. To round off to a number of significant figures, count off the specified number of significant figures, then round based off of rounding rules (down if the next digit is less than 5, up if the digit is 5 or more).

NOTE: Unless a question states otherwise, on IB exams, you are expected to give answers to 3 significant figures.

Rounding rules

SL Core 1.1

There are standardized rules for how to approximate numerical values:

If the digit after the one being rounded off is LESS than 5 (0,1,2,3, or 4), we round down.
If the digit after the one being rounded off is 5 OR MORE (5,6,7,8, or 9), we round up.
1.34∣5→1.35
1.34∣4→1.34

Significant figures

SL Core 1.1

A significant figure is any digit that is not a leading or trailing zero. To round off to a number of significant figures, count off the specified number of significant figures, then round based off of rounding rules (down if the next digit is less than 5, up if the digit is 5 or more).

NOTE: Unless a question states otherwise, on IB exams, you are expected to give answers to 3 significant figures.