Arithmetics with Decimals
Doing arithmetic with decimals is a lot like doing arithmetic with whole
numbers. Read on to see how itâ€™s done.
Part 1: Adding and Subtracting Decimals
PROCEDURE: To add or subtract decimals, line up your numbers vertically so that
the decimal points line up. Then add or subtract the columns from right to left,
carrying or borrowing numbers when necessary.
SAMPLE PROBLEM: Add the following numbers: 3.1415 and 2.96.
Step1: Line up the numbers
vertically so that the decimal points
line up.

Step 2: Add the columns from right to left,
carrying when necessary.

The sum is 6.1015.
Part 2: Multiplying Decimal Numbers
PROCEDURE: To multiply decimal numbers, align the numbers vertically and put
the number with the most digits on top. Multiply the top number by the bottom
number, just like you would multiply whole numbers. Then count the total
number of decimal places in both of the multipliers. In your product, move the
decimal point to the left the same number of places as there are in the
multipliers.
SAMPLE PROBLEM: What is 1.12 Ã— 2.3?
Step 1: Align the
numbers vertically,
with the longer number
on top, and multiply.

Step 2: Count the total
number of decimal
places in both numbers
being multiplied.
There is a total of 3 decimal places. 
Step 3: Because there is a
total of 3 decimal places in
your numbers, move the
decimal point in your
product 3 places to the left.

The product of 1.12 and 2.3 is 2.576.
Part 3: Dividing Decimal Numbers
PROCEDURE: To divide decimal numbers, move the decimal point in the divisor
to the right until it is a whole number. Then move the decimal point in the
dividend to the right the same number of places. Place a decimal point in the
quotient directly above the decimal point in the dividend. Finally, divide as with
whole numbers.
SAMPLE PROBLEM:
Step 1: Move the decimal point in the
divisor to the right until it is a whole
number.

Step 2: Move the decimal point in the
dividend to the right the same number
of places, and place a decimal point
above it in the quotient.

Step 3: Divide as with whole numbers.

