## Decimals

This lesson shows the basics of adding, subtracting, multiplying and dividing decimals. An example of each type is given.

transcript:

Welcome to Your Tutor Online video podcast. In this lesson, you’ll learn how to add, subtract, multiply, and divide decimals. First let’s look at adding and subtracting. If you need to add or subtract decimals, simply rewrite the problem so that the decimal points are lined up with one another.

So we’re going to put the decimals so that they are right underneath each other, the 12 to the left of the decimal, the 2 to the right of the decimal. Add a zero wherever there is blank space after you rewrite the problem. So you have a 0 here, and a 0 here. Now we’re going to put our decimal lined up again in the answer line. And now we’re just going to add like normal. 0 and 3 is 3. 4, 5, and 1. So our final answer is 15.43.

Subtracting is done the same way. You’re just going to move the decimal underneath the other number so that all the decimals are lined up. You have a 2 on the left of the decimal and a 3, 7 to the right. We’re going to fill in all the blank spaces with 0. And we’re going to fill in the decimal on our answer line underneath the other decimals. Now we just subtract like we normally would. The decimals are exactly where it used to be and this is our final answer: 11.73.

When you multiply decimals, line up the two numbers so that their right most digits line up. So we just now put 3, 7 all the way to the right, over here.

Ignore the decimal for now, and just multiply like you normally would. Okay, now that we have our answer for multiplication, we’ll now go back to the original numbers we are multiplying together and count the number of digits to the right of the decimal place. In this number we have 1 number to the right of the decimal place and then this one, we have 2. So altogether, there are 3 numbers to the right of the decimal place. Only count zeroes if there is a non-zero to the right of it.

Now we’re going to move the decimal, 3 places starting from the right. And it goes right here. So our final answer is 192.918.

When we divide, we’re going to rewrite the problems that we have our long division box. First number is those inside the division box, and the second numbers go outside the division box. 27. 975 divided by 0.25. Now we want to look at the number that’s outside the division box if it has any decimals in it, we want to move that decimal to the right until all non-zero numbers are on the left of the decimal.

Here we moved it twice. Move the decimal of the number inside the box the same number of times that you moved the decimal for the number outside. So I’ll move it twice.

So we can rewrite this problem with 25 on the outside and 2797.5 on the inside. We’re going to take this decimal and put it directly above it and that’s where your decimal will be for your answer. Now you just divide like you normally would. So the decimal we drew is automatically in the right space. And our final answer is 111.9.

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