For more information, please see full course syllabus of Basic Math

For more information, please see full course syllabus of Basic Math

### Multiplying Decimals

#### Related Links

- When multiplying decimals, multiply the numbers without worrying about the decimal
- Count the total number of decimal places to the right of the decimal point from the numbers you multiplied
- Place the decimal point in front of that many places

### Multiplying Decimals

- 38.5 ×8.50

- 30.3 ×20.75

- 18.5 ×12.25

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

### Multiplying Decimals

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

- Intro 0:00
- Multiply the Decimals 0:05
- Methods for Multiplying Decimals
- Example: 1.1 x 6
- Extra Example 1: Multiplying Decimals 1:51
- Extra Example 2: Work Money 2:49
- Extra Example 3: Multiplying Decimals 5:45
- Extra Example 4: Multiplying Decimals 7:46

### Basic Math Online Course

### Transcription: Multiplying Decimals

*Welcome back to Educator.com; this lesson is on multiplying decimals.*0003

*When you multiply decimals together, it is very different than when you are adding and subtracting decimals.*0007

*The rules are very different; try not to get confused between the two.*0015

*Remember when you add and subtract the decimals, you have to line up the decimal point.*0020

*Then you add and subtract.*0025

*Then you bring the decimal point straight down into the answer.*0026

*When you multiply decimals, you don't worry about the decimal point at all.*0030

*If I am going to multiply two numbers, let's say 1.1 and 6.*0038

*I don't have to line up the decimal point; make sure you don't do that.*0048

*All you have to do is multiply the numbers without having any consideration for the decimal point.*0051

*I am just going to ignore it; I am going to multiply this.*0058

*It is going to be 6; and then 6; 66.*0061

*What you do is you count the total number of decimal places from the numbers you multiplied.*0066

*From these two numbers, this one and this one,*0071

*you are going to count to see how many numbers are behind the decimal point.*0074

*Here I have one number.*0080

*Here I have none because the decimal point is behind the 6.*0082

*From these two numbers, from 1.1 and 6, I only have one number behind the decimal point.*0087

*I go to my answer; I place one number behind the decimal point.*0098

*The last number is 6; I am going to put the decimal point right there, 6.6.*0103

*Let's do a few examples, 0.2 times 0.6.*0111

*Again I am going to multiply the numbers without considering the decimal points.*0117

*6 times 2 is 12.*0126

*I don't have to multiply those 0s together; it is just 12.*0129

*From this number, from these two numbers, the two numbers that I multiplied,*0134

*I am going to see how many numbers I have behind the decimal point.*0138

*From this number, I have one; from this number, I have another one.*0143

*I have two total; I go to my answer.*0147

*I am going to place two numbers behind the decimal point.*0151

*It is going to become 0.12 or 0.12 or 0.12.*0155

*I can put a 0 up here too.*0161

*This is the whole number; we don't have any whole numbers; it is just 0.*0163

*Another example, if Susan works 25.5 hours per week and she earns*0170

*9 dollars and 40 cents an hour, how much does she earn in a week?*0177

*This is how many hours she works in a week.*0184

*This is how much she earns per hour.*0186

*To figure out how much she earns in a whole week,*0189

*I have to multiply how many hours she worked with how much she makes per hour.*0191

*It is going to be 25.5 times 9 dollars and 40 cents.*0200

*Again when I multiply these numbers, I am just going to line up the numbers.*0210

*I don't care about the decimal point.*0215

*25.5 times 9.40; you are just lining up the numbers.*0218

*Let's multiply the 0; 0 times 0 is going to be all 0s.*0232

*I am just going to move on to the next number.*0237

*4 times 5 is 20; this is 22; 8, 9, 10.*0238

*9 times 5 is 45; 45... that is 49; 18... that is 22.*0248

*These are just 0s here; it is 0, 0, 7, 9, 3, and 2.*0266

*Here is my answer when I multiply these two numbers together.*0276

*Now I have to look at my decimal point.*0280

*The first number, I look at these two numbers, the two numbers that I multiplied.*0284

*I have one number here behind the decimal point and I have two numbers here.*0288

*How many numbers do I have total?--I have three.*0295

*I go to my answer; I count three numbers.*0300

*Make sure that I have three numbers behind my decimal point.*0305

*It is going to be 237.7.*0311

*I am dealing with money here because I am trying to figure out how much she earns in a week.*0317

*This is going to be in money; I am going to have a dollar sign.*0323

*This becomes 239 dollars and 70 cents.*0330

*This is how much she is going to earn in a week.*0338

*The next example, I have 0.21 times 2.1.*0346

*0.21 or I can read this as 21 hundredths because I have two numbers.*0356

*This is tenths; this is hundredths.*0363

*This would be 21 hundredths times 2.1.*0365

*Again I am not going to line up the decimal point; 2.1 or 2 and 1 tenths.*0372

*When I multiply this out, ignore the decimal point.*0383

*2 times 1; write that here; that is 2; 2 times 2 is 4.*0389

*You don't have to look at this number.*0395

*If you want, you can just write that down.*0397

*1 times 0 is 0; that goes there; then I add these down.*0399

*1 plus nothing is 1; 2 plus 2 is 4; this is 4.*0406

*Now I look at my numbers; how many numbers do I have behind decimal points?*0413

*Here I have two; here I have another one; I have three total.*0421

*I am going to go to my answer; I am going to count one, two, three.*0428

*My answer, I have to make sure that there is going to be three numbers,*0436

*the same number of numbers behind this decimal point.*0439

*It is going to be 0.441 or 0.441.*0442

*You can read this as 441 thousandths because I have three numbers and this is the thousandths place.*0451

*This is my answer when I multiply 0.21 times 2.1.*0460

*The fourth example, I am going to multiply these two numbers, 4.08 and 1.35.*0468

*4 and 8 hundredths... again when I multiply these decimals together, I am just going to ignore my decimal points.*0479

*I am just going to line up the numbers just like I do when I multiply whole numbers.*0488

*This just happens to line up because there is the same number of numbers.*0495

*Multiply this out; 8 times 5 is 40; 0, 4; this is 20.*0502

*This is 24, 0, 2; this is 12 here; this is 8, 0, and 4.*0512

*I add them down; 0; this is 8; this is 10.*0528

*2, 4, 5; this is also 5.*0539

*From here, after I multiply my two numbers, I am going to look at the actual numbers that I multiplied.*0545

*I am going to count how many numbers I have behind decimal points.*0554

*For this one, I have two numbers behind the decimal point.*0558

*Here I also have two; total behind the decimal points, I have four numbers.*0562

*You look at just these two numbers that you multiplied together.*0570

*I have four numbers total behind decimal points; I go to my answer.*0574

*I make sure that there is four numbers behind the decimal point.*0579

*That is going to help me place the decimal point.*0583

*One, two, three, four; there is four numbers; place the decimal point right there.*0587

*Since there is four numbers behind decimal points here,*0595

*there has to be four numbers behind the decimal point in the answer.*0598

*It is going to be 5.5080.*0601

*Or this number, it is a 0 at the end of a number behind the decimal point.*0605

*I can just drop it if I want.*0609

*Or you can leave it; it doesn't matter.*0611

*It could be 5 and 508 thousandths.*0613

*Either way, this can be the answer or this can be the answer.*0620

*That is it for this lesson on multiplying decimals; thank you for watching Educator.com.*0626

0 answers

Post by amera arshed on November 16, 2013

so basically with your answer you count how many # were behind the decimal and that is how many you count over on your answer and well thats it

4 answers

Last reply by: Johnathon Kocher

Sat Nov 22, 2014 4:03 PM

Post by Amera Arshed on November 16, 2013

I think educator makes math easier. Ã°Å¸â€™Â¯%

1 answer

Last reply by: amera arshed

Sat Nov 16, 2013 7:25 PM

Post by binti farah on January 17, 2013

I love decimals

2 answers

Last reply by: viet vu

Tue Jan 18, 2011 11:14 PM

Post by Lahdan Rahmati on January 17, 2011

shouldn't it be 441 thousandths ?