Adding decimals - 1 | Year 6 Mathematics PDF Download

Choosing a method

• When asked to perform a calculation for addition, subtraction, multiplication, or division, we often decide whether to do it 'mentally' or use a 'formal' written method.
• It is important to practice both types of calculations and understand when a mental method can provide a quick shortcut by writing down the answer directly, or when the numbers require an effective written method using 'pencil and paper', where we set out our work in columns based on the value of each digit.

Examples

Example 1: What is 6.268 + 7.894?
Sol: Set out the calculation, ensuring each digit is in the correct column based on its place value, and that the decimal points are aligned.
Start with the thousandths column: 8 thousandths plus 4 thousandths equals 12 thousandths, which is 1 hundredth and 2 thousandths.
Move to the hundredths column: 6 hundredths plus 9 hundredths plus the extra 1 hundredth equals 16 hundredths, which is 1 tenth and 6 hundredths.
Move to the tenths column: 2 tenths plus 8 tenths plus the extra tenth equals 11 tenths, which is 1 one and 1 tenth.
Move to the ones column: 6 ones plus 7 ones plus the extra one equals 14 ones, which is 1 ten and 4 ones.

Example 2: What is 2.63 + 4.15?
Sol: Set out the calculation, ensuring each digit is lined up in the correct column based on its place value, and that the decimal points are directly underneath one another.
Starting with the column with the least place value on the right, the hundredths column in this example: 3 hundredths plus 5 hundredths equals 8 hundredths.
Moving to the tenths column: 6 tenths plus 1 tenth equals 7 tenths.
Finally, moving to the ones column: 2 ones plus 4 ones equals 6 ones.