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Rounding Decimals

Objectives

To be able to round decimals up or down to the nearest whole number and to understand mathematical terms such as ‘1-place decimals’.

Resources

Abacus 4 Textbooks 2 & 3 | Squared paper | Rounding Decimals (MyMaths)

Today's Lesson

Main Activity

For the mental warm-up, repeat the exercise from Lesson Two, using ten different numbers.

Turn to page 22 in Abacus 4 Textbook 3.

This page introduces the term ‘2-place decimals’. However, your student has been working with these numbers before; this is simply adding new mathematical vocabulary.

Just as with whole numbers, where 2-digit numbers will round up to the nearest hundred once they are 50 or more, in exactly the same way, the decimals will round up to the next whole number provided the digits after the decimal point are .50 or more. .49 or less will round down to the previous whole number.

For example:

3.52 rounds up to 4

3.47 rounds down to 3

You could use a place value chart to enhance their understanding.

For Example 3.52

As we are rounding to the nearest whole number (the ones column), we look at the column to the right (in this case the tenths column).

As the digit in this column is 5, we round UP. The 3 ones become 4 ones so the answer would be 4.

Once you feel that your student is comfortable with the concepts, ask them to copy and complete the page. Encourage your student to attempt the problems independently.

Then discuss the ‘Think’ question together, using 2-place decimals, rather than 1-place decimals.

Citations

[1] app.mymaths.co.uk