Multiplication of Decimals

A decimal point indicates that a number is not a whole number. Fractions can all be written as decimals. Multiplying decimals is easier than it might appear, and does not necessarily require a calculator. Simply treat the decimals as whole numbers, then worry about where to put the decimal point after multiplication is complete. Whole numbers can also be multiplied by decimals in the same way.

Instructions

1. Line up the numbers on top of each other, aligning the numerals on the far right-hand side. Do not align the decimal points. For example, 2.25 times 3.5 would be written as: 2.25x 3.5

2. Multiply the value on the top by the value on the bottom. Multiply the far right-hand number by all the numbers in the upper value, starting with the right (i.e., 5). Then move to the number to the immediate left of the one you just multiplied (i.e., 3). Ignore the decimal points. 2.25x 3.5equals1125 + 6750 = 7875

3. Count how many numbers you have following decimal points in both the top and bottom values. (In our example, this equals three.) That is how many numbers will follow the decimal point in your answer. So in our example, the final answer would be 7.875.

Tips & Warnings

• When adding whole numbers to decimals, you do not need to add a decimal point to the whole number. For instance, you do not need to write 3 as 3.0.

• When multiplying decimals by 10 or a multiple of 10, simply move the decimal point once to the right for every zero. For instance, 10 x 2.345 becomes 23.45, and 100 x 2.345 becomes 234.5.