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### Course: Arithmetic (all content) > Unit 6

Lesson 9: Adding and subtracting decimals word problems# Adding decimals word problem

Adding decimals is an essential math skill. In this example, we find the total weight of newborn twins. Nadia weighs 7.27 pounds, and Vanessa weighs 8.34 pounds. By carefully lining up the decimals and adding the numbers, we discover their combined weight is 15.61 pounds. Created by Sal Khan.

## Want to join the conversation?

- I just realized, decimals and whole numbers are very different. If you put a 0 in a decimal, it makes no difference, but in a whole number, it makes so much difference.(21 votes)
- True. 0.0 is just that--0. The same goes for 1.0, 2.0 3.0...they're just 1, 2, 3...; but without the decimal point they're 10, 20, 30...; 00 is still 0 though. Sorry 0!(13 votes)

- more hints because some people dont understand it well from the understanding of the hints(12 votes)
- * I agree with you sometimes it happens with me also and I think that it happens with everyone if true then like and tell

Give reply*(1 vote)

- hello, math is very frustrating for me and I usually end up depressed afterwards. Does anybody have tips to help me stay happy about math?(8 votes)
- First, make sure you have memorized your basic math facts. That's all of the addition/subtraction and multiplication/division facts up to 10+10 and 10x10.

Next, figure out which things you are not understanding as well as you'd like and practice them. For example, I found your question in the "6th Grade" section so I assume something about 6th grade math is causing problems. Did you find 5th grade math OK? If not, use Khan Academy to review and relearn 5th grade math. If you find things in that section that are confusing, try the 4th grade section. As you review and relearn previous years math, you'll find the current year getting easier.

Will it take time? Yes. But it will be worth it. As ellajahcat says, Math is important for life. No matter what type of job you end up in, you'll need math.(9 votes)

- do you always have to line up the decimais(2 votes)
- It's less prone to mistakes, as long as the decimal places are added to the correct decimal place it's alright, but when they aren't lined up the chances of making a mistake increases.(17 votes)

- isn't there's a 0 in every number?(4 votes)
- You can put it that way, yes. There will be a zero in every number.

For example, 1 can be expressed as 1.0, 1.00, 1.000, etc. It goes the same with all other numbers. Zeros don't have any effect on numbers, but**only**if a decimal point is added. If we forget to do that, for example, 1 to 10, it's a completely different number.(9 votes)

- i am still having a hard time because it dose not make sense to me at all so please tell me the meaning of this please make an different video cuz i having hard time.(6 votes)
- I think the word 'Decimal' is Latin, correct?(6 votes)
- Kind of. Decimal comes from the word "Deci", which is Latin for 10.(5 votes)

*Whats the***math**`behind`

math?(6 votes)- What would happen if the decimals are not lined up?(3 votes)
- Then you'd get the wrong number. For instance,

_65.74

+_3.76

This would equal 69.5 if you add line by line.

65.74

+__3.76

Adding line by line gets you 66.1.2 which isn't exactly a valid number, since you can't have a decimal after the decimal.(3 votes)

## Video transcript

On Saturday, William's
parents gave birth to twins and named them
Nadia and Vanessa. When they were first born,
Nadia weighed 7.27 pounds and was 21.5 inches tall, and
Vanessa weighed 8.34 pounds. How much did the
babies weigh in total? So they tell us Nadia weighed
7.27 and Vanessa weighed 8.34. We have to add those up. And really, they
just gave us this. The length of Nadia at birth
really is a distraction, just so that we just
don't mindlessly add any numbers we see. So this is really
unnecessary information just to distract us. So we need to add Nadia's
birth weight plus Vanessa's. So it's 7.27. So 7.27 plus 8.34. And it's always important
that we line up the decimal. And I'd like to do
the decimal first. So it's 8.34. And we'll just add these two up. So 7 plus 4, and this is
really 7/100 plus 4/100 is 11/100, which is the same
thing as 1/100 and 1/10. 1/10 plus 2/10
plus 3/10 is 6/10. We've got our decimal
sign right over there. And then 7 plus 8 is
15, or you could even say it's five 1's and one 10. And we're done. They weighed 15.61
pounds in total.