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Course: 6th grade > Unit 4
Lesson 3: Powers of fractions and decimalsExponents of decimals
Exponents of decimals can be calculated by multiplying the decimal number by itself as many times as the exponent indicates. When multiplying decimals, count the total number of digits to the right of the decimal points in both numbers and place the same number of digits to the right of the decimal point in the product.
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how do you do 10 to the 12 power(13 votes)
10 to the 12th power would be 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10. The answer would be 1000000000000(40 votes)
At the end of the video sals says another way to think about it is "9 tenths of 9 tenths is 81 hundreths"
But isn't 0.9/0.9 = 1?(7 votes)- "Of" refers to multiplication; He's saying 0.9*0.9 = 0.81(25 votes)
0.9 x 0.9= 0.81? I see the math and understand how it is done. But 0.81 is smaller than 0.90? How does a bigger number (0.9) multiplied by itself ended up being smaller?(11 votes)
I think it's because they are decimals, so when they are multiplied, they go backwards instead of forwards. Is that helpful at all? It probably isn't. I hope I didn't confuse you more!(13 votes)
- A lot of the time when I'm stuck on an equation I tend to watch the video a few times and sometimes it still doesn't help because the person on the video does a lot of the math in their head and that's where it loses me is there any way for me to get one-on-one help?(8 votes)
Hi Christine,
Yes, I have that problem sometimes too. Sal (in the voiceover) usually does the mental math faster than we can catch up. Unfortunately there is no feature here that you can get one-on-one help. (or not that I know of)
What I would suggest it to pause the video and try to do the math yourself on a piece of paper or in your head. If you don't get that math, you could try searching up how to do it here on Khan Academy.(10 votes)
I really hate how he doesn't fully explain why you don't add the same amount of zeros to the second example here. You moved the decimal two spots to get 0.04 after multiplying 0.2 x 0.2. But why don't you do that for 0.9?(5 votes)
You need to count decimal places needed. In both cases, the numbers being multiplied have 1 decimal place. 1+1 = 2 decimal places in your answer.
2x2 = 4
Since this is one digit, you need to put a zero in front of the 4 to create the 2 decimal place: 0.04
9x9 = 81
This is already a 2 digit number. So, the decimal point goes in front of the 8: 0.81
Note: This is no different then if you multiplied 0.2 x 0.12
There are 3 decimal digits. So, the answer becomes 0.024
You may find it helpful to review the lessons on multiplying decimal numbers.(14 votes)
- What is 0 to the power of 0?(7 votes)
0 to the power of 0 = 1(2 votes)
- how do you use a exponent when using a fraction, for example (2/5) and 3 is a exponent.(5 votes)
You have to convert the fraction (2/5) to a decimal (0.4) than you can use the exponent (3) so 0.4x0.4x0.4= 0.064 hope this helps(2 votes)
what is 24 to the power of 5(4 votes)- Sorry, but I can not just give you the answer so I will tell you how to get the answer so you can also write out 24 to the power of 5 like this "24 Times 24 times 24 times 24 times 24 =" so exponents are pretty much multiplying one number as many times as the exponent says to. I hope this helped.(4 votes)
- Would zero to the zeroth power be one or zero?(5 votes)
- i think it would be just a 0(2 votes)
- I physically cannot comprehend why 0.2^3 (zero point two to the third power) isn't .8 and is 0.008. Even the explanation he barely provided didn't make sense. Why is anything decreasing in value after it's been multiplied? I know its a decimal and that's the reason but I don't get why it gains zeroes out of nowhere.(3 votes)
Good question. The2in0.2is the tenths place value, so this number is in tenths. So when multiplying by itself you multiply tenths by tenths and this will become hundredths, and so on.
You can think of any decimal numbers less than one, such as0.2, as an equivalent power-of-ten fraction:2/10!
Recall the property of exponent of fractions (this arises from how fraction multiplication works):(a/b)^n = (a^n)/(b^n).
In steps:
0.2^1 = (2^1)/(10^1) = 2/10 = 0.2
0.2^2 = (2^2)/(10^2) = 4/100 = 0.04
0.2^3 = (2^3)/(10^3) = 8/1000 = 0.008
0.2^4 = (2^4)/(10^4) = 16/10000 = 0.0016
You can see how the denominator gets multiplied by 10, which translates to moving 1 decimal place to the left, or adding a 0. Hopefully now you can see why this is the case.
I hope this helps; I have no idea if it will.(5 votes)
Video transcript
- [Instructor] What we're
going to do in this video is get some practice evaluating
exponents of decimals. So let's say that I have
0.2 to the third power. Pause this video, see
if you can figure out what that is going to be. Well, this would just mean
that if I take something to the third power, that means
I take three of that number and I multiply them together. So it's 0.2 times 0.2 times 0.2. Well, what is this going to be equal to? Well, if I take 0.2 times
0.2, that is going to be 0.04. One way to think about
it, two times two is four and then I have one
number behind the decimal to the right of the decimal here. I have another digit to
the right of the decimal right over here, so my product
is going to have two digits to the right of the
decimal, so it'd be 0.04. And then if I were to
multiply that times 0.2, so if I were to multiply that together what is that going to be equal to? Well, four times two is equal to eight and now I have one, two, three numbers to the right of the decimal point, so my product is going to
have one, two, three numbers to the right of the decimal point. So now that we've had a little
bit of practice with that, let's do another example. So let's say that I were to
ask you, what is 0.9 squared? Pause this video and see
if you can figure that out. All right, well this is just
going to be 0.9 times 0.9. And what's that going to be equal to? Well, you could just say nine times nine is going to be equal to
81, and so, let's see, in the two numbers that I'm multiplying I have a total of one, two
numbers, or two digits, to the right of the decimal point so my answer's going
to have one, two digits to the right of the decimal point. So put the decimal right over there and I'll put the zero, so 0.81. Another way to think about it
is nine-tenths of nine-tenths is 81 hundredths, but there you go. Using exponents, or taking
exponents of decimals is the same as when we're
taking it of integers. It's just in this case you just have to do a little bit of decimal multiplication.