Review of Introductory Mathematics
Addition and Subtraction of Decimals
When adding or subtracting decimals, each number must be placed to align the decimal points.
When necessary, zeros are used as place holders to make this possible. Then the operation of
addition or subtraction is performed.
0.423 + 1.562 + 0.0736 + 0.2 =
Align decimal points
0.832 - 0.0357 =
When multiplying decimals, the decimal points do not have to be aligned. Rather, it is important
to accurately position the decimal point in the product. To position the decimal in the product,
the total number of digits to the right of the decimals in the numbers being multiplied must be
equal to the number of digits to the right of the decimal in the product. This is best illustrated
in the following examples:
Multiply numbers without inserting decimal in the products.
Sum the number of digits to the right of the decimal in all of the numbers
Position the decimal in the product so the number of digits to the right of
the decimal equals the total number of digits to the right of the decimal in
the numbers multiplied (from Step 2).