Adding and Subtracting Decimals and Whole Numbers Math with Mr J

Welcome to Math with Mr. In this video, I'm going to cover how to add and subtract decimals and whole numbers. We will start with adding and then move on to subtracting. So, let's get right into it here. Now, whenever we have an addition problem involving decimal and whole number, so either decimal plus whole number or whole number plus decimal, we use the same steps that we use when adding two decimals. We line up the decimals, use placeholder zeros, and add. Let's jump into number one where we have 17 and 43 hundredths plus 8. So, let's set this problem up by lining up the decimals. So, we have 17 and 43 hundreds plus 8. Now, how do we line up the decimal for our whole number here? 8. Well, remember decimals come after whole number. They come after the ones place. So, the decimal is right here for eight. So we have eight and then the decimal. So our decimals are lined up now and our problem is lined up. But it does look little offset since 17 and 43 hundreds goes to the hundredth's place and 8 only has digit in the ones place. So we can use two placeholder zeros after the decimal. That way 8 goes to the hundredth's place as well. Now those two zeros to the right of the decimal are not changing the value of eight. That still has value of eight. So we're able to do this. Now our problem looks more lined up. And now we can add. We will start with the hundredth's place. So 3 + 0 gives us 3. 4 + 0 gives us 4. Bring the decimal straight down. It's lined up throughout the entire problem. Then we have 7 + 8, that's 15. And then 1 + 1 gives us 2. So we end up with 25 and 43 hundreds. So 17 and 43 hundreds + 8 equ= 25 and 43 hundreds. Now, whenever we have an addition problem involving decimal and whole number, the decimal digits are going to stay the same. So, for example, number one, we end up with 43 hundreds. That's because 8 didn't have any decimal digits, so it's just going to be again 43 hundreds. Basically, we're just adding the whole numbers. 17 + 8 is 25 and then again we have 43 hundreds. So something to keep in mind whenever we are adding decimal and whole number. Moving on to number two, we have 126 plus 35 and 9/10. Let's set this problem up by lining up the decimals. The decimal goes after the whole number after the ones place. So for 126 it goes after the six. So we have decimal and then we line up 35 and 9/10. So the decimals are now lined up. So let's use placeholder zero in the 10th's place for 126. Now both of our numbers go to the tenth's place and we can add. We will start by adding the tenth's place. So 0 + 9 gives us 9. Bring the decimal straight down. Then we have 6 + 5, that's 11. Then we have 1 + 2 is 3 + 3 is 6. And then 1 in the hundred's place. So we end up with 161. and 9/10. So 126 + 35 and 9/10 equals 161 and 9/10. So there's how to add decimals and whole numbers. Let's move on to subtraction. So here's our section on subtracting whole numbers and decimals. So either decimal minus whole number or whole number minus decimal. Now whenever we have subtraction problem involving decimal and whole number, we use the same steps we use when subtracting two decimals. Line up the decimals, use placeholder zeros if necessary, and subtract. Let's jump into number one where we have 13 - 4 and 64 hundreds. Our first step is going to be to set this problem up by lining up the decimals. Now, we have whole number here, 13. Remember, the decimal point goes to the right of the ones place, to the right of the whole number. So, we can put decimal point right here for 13 that we can use to line this problem up. Typically, if we just have whole number, we write it without decimal point. But here we are using the decimal point to line up the problem. So we are including it. Now we can set this up. So we have 13 decimal point minus 4 and 64 hundreds. Now at this point do not just bring the six and the four straight down into the answer. There are actually zeros above those digits. So, we will need to go through the subtraction process. So, our problem is lined up. The decimals are lined up, but it does look little offset here. So, we can use placeholder zeros to make this look little more lined up and organized. And we actually need these zeros in order to go through the subtraction process. So since 4 and 64 hundredths goes to the hundredth's place, we need two zeros right here. That way 13 goes to the hundredth's place as well. Now those zeros to the right of the decimal point are not changing the value of that 13. That's still 13. So we're able to do this. We're not changing the value of anything here. Now we're ready to subtract. So, let's start with the hundredth's place. We have 0 - 4, which we're going to need to borrow. So, we need to go all the way over to the three. Borrow. This is now 2. Then, we have 10 here, which is now 9. And then we end up with 10 - 4, which gives us 6. Then we have 9 - 6, that gives us three. Then we have our decimal. Bring the decimal straight down into the answer. The decimal is lined up throughout the entire problem. Then we have 2 - 4 which we need to borrow. So we borrow from this 1 which is now zero. And now we have 12 - 4 which gives us 8. And this is our final answer 8 and 36 hundreds. So 13 - 4 and 64 hundredths equals 8 and 36 hundreds. Let's move on to number two where we have 28 and 8/10 minus 9. So let's set this problem up by lining up the decimals. Now for our whole number 9, the decimal goes right here. So we have 28 and 8/10 minus 9 and then the decimal point. Now we need placeholder zero. But before we write that in, notice the difference between number one and number two. For number one, we subtracted from the placeholder zeros. So we needed to borrow. For number two, we're going to end up with 8 minus 0 in the 10th's place, which gives us eight. So, we will end up with 8 in the 10th's place of our answer. So, depending on if we have whole number minus decimal or decimal minus whole number, that impacts how these problems are going to work out. So something to keep in mind since 28 and 8/10th goes to the 10th's place let's use placeholder zero right here. That way 9 goes to the 10th's place as well. And now we can subtract. So we start with 8 - 0 in the 10th's place. That gives us 8. Then we can bring the decimal straight down. Next we have 8 - 9 which we need to borrow here. So this two is now one and we have 18 - 9 that gives us 9 and then we have 1. So our final answer 19 and 8/10. So 28 and 810 - 9 gives us 19 and 8/10. So there you have it. There's how to add and subtract decimals and whole numbers. hope that helped. Thanks so much for watching. Until next time, peace.