# Accuracy and Rounding

Scheme of work: GCSE Foundation: Year 10: Term 3: Accuracy and Rounding

#### Prerequisite Knowledge

• Recognise the value of a digit using the place value table.
• Round numbers to the nearest integer or given degree of accuracy not including decimal place or significant figure
• Calculate square numbers up to 12 x 12.

#### Success Criteria

• use standard units of mass, length, time, money and other measures (including standard compound measures) using decimal quantities where appropriate
• round numbers and measures to an appropriate degree of accuracy (e.g. to a specified number of decimal places or significant figures
• estimate answers; check calculations using approximation and estimation, including answers obtained using technology
• use inequality notation to specify simple error intervals due to truncation or rounding
• apply and interpret limits of accuracy

#### Key Concepts

• When rounding to the nearest ten, decimal place or significant figure students need to visualise the value at a position along the number line. For instance, 37 to the nearest 10 rounds to 40 and 5.62 to 1 decimal place rounds to 5.6.
• When a value is exactly halfway, for instance 15 to the nearest 10, by definition it is rounded up to 20.
• To estimate a solution it is necessary to round values to 1 significant figure in the first instance. However, students need to apply their knowledge of square numbers when estimating roots.

#### Common Misconceptions

• When rounding to a significant figure the values that are less significant become zero rather than being omitted. For instance, 435 to 1 s.f. becomes 400 rather than 4.
• Students often have difficulty calculating the upper bound of a rounded value. For instance the upper bound for a number rounded to the nearest 10 as 20 is 25 not 24.999.
• When using inequality notation to describe the limits of accuracy there can be confusion with the direction of the symbols.

## One thought on “Accuracy and Rounding”

1. ##### Munaro Makozvvosays:

Very informative and educative.

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