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### Course: Arithmetic > Unit 12

Lesson 1: Adding decimals intro# Adding decimals

Start with simple problems like 0.2 + 0.4 and build to more complex problems like 10.3 + 36.75.

This article is designed to help you learn how to add decimals by letting you jump in and give it a try without being shown how to do it first.

The problems go from easier to more difficult, and along the way, there are examples and explanations for the times you get stuck. You'll learn the most if you look at the times you're confused as chances to learn!

Let's start by adding two tenths together.

# Section 1: Adding tenths less than one

Beautiful, let's move on to problems with whole numbers and tenths.

# Section 2: Adding whole numbers and tenths

Excellent, next up are problems where both numbers have a whole number and a tenth.

# Section 3: Adding tenths greater than one

Rockin'! Let's move on to adding hundredths.

# Section 4: Adding hundredths

Sweet, now we're ready to solve problems with hundredths, tenths, and whole numbers.

# Section 5: Adding whole numbers, tenths, and hundredths

Great, let's finish with a few more challenging problems.

# Section 6: Challenge problems

## Want to join the conversation?

- Will every chapter of khanacademy have the set of questions(168 votes)
**Yes**. Probably 99% of chapters in math at Khan Academy have exercises. 👍(208 votes)

- I have a something i was confused about. In section 4 on the 4th question it has 0.61 + 0.2 I said it was 63 (61 + 2) but it said it was 81. I don't understand this. In the example it showing it's add 20, but it's not 20, it's 2. If it was 20 it would be 0.61 + 0.20 and it wasn't.

In an earlier question there was 0.5 + 0.4 which is 0.9 which makes sense (4 + 5). So why in that 4th section is it changing it to 20? and How do i know that if 0.2 is 20, or just 2?

Thanks,

~Kat(45 votes)- Have a look at the videos and practice questions about tenths, hundreds, thousands, etc, as I think this is where you're getting confused.

0.61 is 6 tenths and 1 hundredth

0.2 is 2 tenths (and 0 hundredths)

So when you add them your answer is 8 tenths (6 + 2) and 1 hundredth (1 + 0), so it is 0.81

0.2 is the same as 0.20 but we don't need to write the extra 0. 0.2 is also the same as 0.2000000 just like 0.61 is the same as 0.610 or 0.61000000

Another way to think of it is that you are adding 61/100 + 20/100 = 81/100

If the question was 0.61 + 0.02 then your answer would be 0.63 but 0.2 is ten times bigger than 0.02

I hope this helps :)(52 votes)

- how do you add 10.01 and 19.001 together what do you get(10 votes)
- To add decimals with different numbers of factors to the right of the decimal point, fill in blank spots with zeros. In your example, add a zero to 10.01 + 0. This doesn't change the value of 10.01. The addition problem is below. Hope it helps.

10.010

+ 19.001

--------------

29.011(62 votes)

- i know this is suppose to make us smarter but why so many questions(28 votes)
- because questions make your brain get smarter.(1 vote)

- why are there so many questions(27 votes)
- because every section has a different set of different problems(6 votes)

- why when I put 6.6 known as 1 in the equation (6.4 + 2=) I got it wrong and they gave e the answer of ... (8.4)?(4 votes)
- 6.4+2 actually = 8.4 because 2+6 = 8 +0.4 = 8.4(38 votes)

- Is the practice graded?(20 votes)
- i am not good at this i need some practice(20 votes)
- who else likes sets of math(11 votes)
- small numbers be like 0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001(9 votes)
- no that's not a small number(3 votes)