Multiply Decimals

Multiplying decimals may look tricky, but it's quite simple if you know how to multiply whole numbers. You can multiply numbers with decimals just as you would multiply whole numbers, as long as you remember to factor in the decimals at the end of the problem. So how do you do it? Follow these steps to find out.

Steps

  1. Line up the numbers on top of each other. If one number has more digits, you can put the number on top of the other. Let's say you're multiplying .43 by .06. Just line one number on top of the other, above the multiplication bar.
  2. Multiply the numbers while ignoring the decimal points. Now, just multiply the numbers as you usually would in ordinary multiplication. Here's how you would multiply .43 and .06:
    • Start by multiplying the 6 in .06 by the 3 in .43 to get 18. Write "8" below the 6 and carry the 1 on top of the 4.
    • Multiply the 6 by the 4 in .43 to get 24. Add 24 to the 1 that was on top of the 4 to get 25. The top row should read 258.
    • When you start multiplying .43 by 0, you'll see that you only get 0, so there's no need to write anything down.
    • The answer is 258 while you're ignoring the decimal points.
  3. Count up all of the number of digits that are located at the right side of the decimal points of the multiples. There are two numbers to the right of .43 (4 and 3), and there are two numbers to the right of .06 (0 and 6). Therefore, add 2 and 2 to get 4, the total amount of numbers to the right of both decimal points.
  4. Move the decimal point of the whole number to the right that number of times. Since you counted 4 numbers, start with the decimal point at the end of the whole number 258, and move it over four times to the right starting to the right of the 8. You'll end up moving it one space right past the 2 in 258.
  5. Fill in the extra space with a zero. Since there's a blank space between the decimal point at the 2, fill it in with a zero. 258 becomes ".0258."
  6. Check your work. If you want to make sure that .43 multiplied by .06 is indeed .0258, you can divide .0258 by .06 to make sure that you get .43. So, .0258 ÷ .06 = .43. You can check your work by dividing the answer by either number to get the other. Therefore, you can divide .0258 by .43 to make sure you get .06. Does it work? .0258 ÷ .43 = .06. You're all done. .43 ÷ .06 = .0258.



Tips

  • Estimate. If the number(s) are too small, like the above problem, then the product will be close to zero.
  • You can also think of it as whole numbers if you don't get integers. Multiply them as whole numbers. Then check by dividing. Then find out where the decimal goes.
  • After moving the decimal point to the front of the no.s move the decimal point a step forward.
  • Multiplying decimals is exactly the same as multiplying integers, except you have to add the correct amount of decimal places at the end.

Warnings

  • Do not line up the decimals! Only align decimal points with addition and subtraction.

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