1A Rounding and estimating

Learning intentions

By the end of this topic you will be able to …

✔ round whole numbers

✔ estimate results of simple calculations

✔ assess the accuracy of estimations.

Place value

• Place value charts can be used to determine the value of each digit in a number.

Rounding

• Rounding a number means to replace it with an approximation that is simpler and easier to use. Using rounded numbers makes calculations less accurate.

➝ ‘Approximately equal’ is shown using the symbol ‘≈’.

• To round to the nearest thousand, place a box around the digit in the thousands place.

➝ If the digit to the right of the box is equal to or greater than 5, round up

➝ If the digit to the right of the box is less than 5, round down

• To round to a number’s leading digit place a box around the first digit and check if the second digit is less than, equal to or greater than 5.