Multiplying decimals means finding the total when one decimal number is taken a certain number of times. It works just like multiplying whole numbers, but you must place the decimal point correctly in the final product.
Each notebook costs $2.45. If you buy 3 notebooks, how much do you spend?
To multiply decimals, first multiply the numbers as if they were whole numbers:
Always line up the numbers by place value, not by the decimal point. Multiply as whole numbers, then place the decimal at the end.
Follow these steps to multiply any two decimals correctly:
Estimate first to see if your answer makes sense. If 8 × 2 = 16, then your product should be close to 16, not 200 or 2.
When multiplying decimals in money problems, you are finding total cost, earnings, or savings when one price or rate repeats several times.
A ticket costs $12.75. If 5 friends buy tickets, how much do they spend altogether?
Multiply $12.75 × 5 = 63.75, so they spend $63.75 total.
Always include the dollar sign and two decimal places in money answers (for cents).
Sometimes decimals show parts of a unit, like meters or feet. Multiplying tells you the total measurement after repeating or scaling that unit.
A board is 1.25 meters long. You need 4 boards of the same length. What is the total length?
Multiply 1.25 × 4 = 5.00, so the total length is 5 meters.
Always label your final answer with the correct unit, such as meters, feet, or inches.
Multiplying decimals is also used to find area when both the length and width are decimal numbers.
A rectangle is 2.4 meters long and 1.5 meters wide. What is its area?
Multiply 2.4 × 1.5 = 3.6, so the area is 3.6 square meters.
The product of two measurements is always in square units, such as square meters (m²) or square feet (ft²).
Multiplying decimals helps when calculating total distance, time, or cost in real-world rate problems.
A car travels 55.6 miles each hour. How far will it travel in 2.5 hours?
Multiply 55.6 × 2.5 = 139.0, so the car travels about 139 miles.
Always check that your answer makes sense. If the car travels about 50 miles per hour for 2 hours, it should go around 100 miles — your estimate helps confirm accuracy.
After multiplying decimals, estimate and round your result to see if it fits the real-world situation.
If you multiply 4.2 × 3.9, estimate 4 × 4 = 16. The product 16.38 makes sense because it is close to the estimate.
Estimation helps you decide whether your answer is reasonable, especially in money or measurement problems.