When performing operations with decimals, lining up the numbers by place value is particularly important for the following operations:
-
Addition: You must align the decimal points to ensure that each number adds correctly by place value (ones, tenths, hundredths, etc.).
-
Subtraction: Similar to addition, you need to line up the decimal points to subtract correctly across the different place values.
In both operations, if the numbers are not lined up correctly by their decimal points, you may arrive at an incorrect sum or difference.
Multiplication and division of decimals do not require lining up by place value; for multiplication, you can multiply the numbers as whole numbers and then place the decimal in the product based on the total number of decimal places in the factors. For division, you can move the decimal as necessary to perform the division and place the decimal in the quotient accordingly.