# How to Multiply Decimals Lesson

Multiplying decimals is important when we are working with grouping items. For example, if we were having a party and each child was getting an eighth (0.125) of a pizza, which is one slice, and there were 24 children coming to the party. We could multiply 0.125 by 24 to determine how many pizzas we would need. Multiplying decimals is similar to multiplying whole numbers, but you need to consider the placement of the decimal point in the result. When we multiply decimals, we ignore the decimals and multiply the numbers as though they were whole numbers. Then we count the number of decimal places in both numbers to determine where the decimal will be placed in the answer. Here’s a step-by-step guide:

1. Ignore the decimals: Treat the decimals as if they are whole numbers and multiply just like you would with whole numbers.
2. Count the total decimal places: Count the total number of decimal places in both the numbers being multiplied. This will help you determine where to place the decimal point in the final answer.
3. Multiply the numbers: Multiply the numbers as if they were whole numbers, ignoring the decimal points.
4. Place the decimal point: Place the decimal point in the result by counting from the right, using the total number of decimal places calculated in step 2.

For example, if we wanted to multiply 3.6 by 0.2, we would multiply 36 by 2 to get 72. Then count the decimal places in the original problem, and notice that there were two decimal places, therefore we move the decimal two places from the right of the number, to get a result of 0.72.

Multiplying a decimal number times a whole number follows the same steps as above. You ignore the decimals, multiply the two numbers, count the decimal places, and place the decimal in the correct location based on the sum of the decimal places.

For example, let’s multiply 24 by 1.25. To start we would multiply 24 times 125, ignoring the decimal places. Then we would count the decimal places and notice that there are two decimal places, so in our final answer we would place the decimal point two places from the right of the number.

Multiplying decimals is really helpful in many real life situations. For example, if we were buying 4 boxes of cookies that each cost \$3.59, we would multiply 4 by 3.59.

Therefore, the total cost of 4 boxes of cookies at \$3.59 each, would cost a total of \$14.36. This can be applied in many different real life scenarios.

Examples

Example 1: Multiply 0.56 and 3.24.

Solution: We would begin by ignoring the decimal places and multiply 56 times 324.

Then we would count the decimal places and notice that there are 4 decimal places in total. We would place the decimal point 4 places from the right of the number, after we multiplied the two whole numbers.

Since 56 x 324 = 18144, and there are 4 decimal places, we place the decimal 4 places from the right of the number, which results in 1.8144.

Therefore 3.24 x 0.56 = 1.8144.

Example 2: If a customer bought 48 cupcakes with each cost \$2.50. How much will the cupcakes cost in total?

Solution: We would begin by ignoring the decimal places and multiply 48 and 250.

Then we would count the decimal places and notice that there are 2 decimal places in total. We would place the decimal place 2 places from the right of the number, after we multiply the two whole numbers.

Since 250 x 48 = 12000, and there are 2 decimal places, we place the decimal 2 places from the right of the number, which results in 120.00.

Therefore 48 x 2.50 = 120.00. Hence, the cost of these 48 cupcakes will be \$120.00.

Example 3: Multiply 0.46 and 0.312.

Solution: We would begin by ignoring the decimal places and multiply 46 times 312.

Then we would count the decimal places and note there are 5 decimal places in total. After we multiply the whole numbers we would place the decimal point 5 places from the right of the number.

Since 312 x 46 = 14352, and there are 5 decimal places, we place the decimal 5 places from the right of the number, which results in 0.14352.

Therefore 0.46 x 0.312 = 0.14352.

FAQs on Multiplying Decimals

1) How do I multiply decimals?

To multiply decimals, treat them as if they are whole numbers, ignore the decimals initially, multiply as usual, and then place the decimal point in the result based on the total number of decimal places in the original numbers.

2) What if the decimals have different decimal places?

Adjust the placement of the decimal point in the final result based on the total number of decimal places in both numbers being multiplied.

3) Can I use the standard multiplication method for decimals?

Yes, you can use the standard multiplication method for decimals. Just be mindful of the decimal placement in the final result.

4) What if one of the numbers is a whole number?

If one of the numbers is a whole number, you can still follow the same steps. The whole number is considered to have a decimal point at the end.

5) How do I know where to place the decimal point in the result?

Count the total number of decimal places in both numbers being multiplied and place the decimal point in the result accordingly.

6) What if there are trailing zeros in the decimals?

Trailing zeros after the decimal point can be ignored when multiplying. They don’t affect the result.