anonymous
  • anonymous
how do i find the LCD?
Mathematics
  • Stacey Warren - Expert brainly.com
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schrodinger
  • schrodinger
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
anonymous
  • anonymous
Find multiples of each the denominators and see which ones they all have in common. Then choose the smallest of those to be your LCD.
anonymous
  • anonymous
For example: Finding the LCD of 2/3, 5/12, and 7/15 we would list multiples of 3, 12 and 15
anonymous
  • anonymous
The other method involves factorizing your denominator

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anonymous
  • anonymous
And is often a bit faster.
anonymous
  • anonymous
so what if i have big number like, 220 and say 100....?
anonymous
  • anonymous
Yeah, that's when factorizing helps. What are the factors of 220?
anonymous
  • anonymous
how do you find the factors?
anonymous
  • anonymous
22 * 10 = 220 (11*2)*(5*2) = 220 So the factors of 220 are 2*2*5*11
anonymous
  • anonymous
oh, ok thanks!!
anonymous
  • anonymous
Does that make sense as to how you break them down?
anonymous
  • anonymous
yea sort of, i'm a little bit rusty when it comes to math....
anonymous
  • anonymous
So now, what are the factors of 100?
anonymous
  • anonymous
Pick two numbers you can multiply to get 100
anonymous
  • anonymous
hold up one second
anonymous
  • anonymous
ten and one??
anonymous
  • anonymous
ten times one is ten.
anonymous
  • anonymous
ok sorry, i ment ten times ten and 1 times 100
anonymous
  • anonymous
yeah, don't bother with 1, it's not useful when factoring, because you can factor infinitely many ones from any number
anonymous
  • anonymous
But \(10\times 10\) is good. So now, what two numbers do you multiply to get 10?
anonymous
  • anonymous
5x2 and 1x10 are the only ones i can think of right off the top of my head
anonymous
  • anonymous
Right, those are the only ones. But again, the 1x10 is not useful. So we'll use 5x2
anonymous
  • anonymous
So that means that \(100 = 10\times 10\) \(100 = (5\times 2)\times (5\times 2)\)
anonymous
  • anonymous
So the factors of 100 are?
anonymous
  • anonymous
10?
anonymous
  • anonymous
No. 2*2*5*5
anonymous
  • anonymous
sorry, like i said, a bit rusty
anonymous
  • anonymous
You take each number in your fully factored form those are your factors
anonymous
  • anonymous
In this case we had 2*5*2*5 = 100, so 2, 2, 5, 5 would be our factors.
anonymous
  • anonymous
oh, wow, thank you so much for your help!!!
anonymous
  • anonymous
Ok, so now we take the factors of 100 and the factors of 220 and compare them: 100= 2*2 * 5*5 220= 2*2 * 5 * 11
anonymous
  • anonymous
and the lowest is two, so the LCD would be 2??
anonymous
  • anonymous
No, that's the LCF
anonymous
  • anonymous
ok so whats the LCD then?
anonymous
  • anonymous
The lowest common factor is 2, but the lowest common divisor is actually bigger than 100, or 220
anonymous
  • anonymous
And we see that if we want them to have the same factors, we need a 11 times 100 and a 5 times 220
anonymous
  • anonymous
What is 11 * 100?
anonymous
  • anonymous
im looking for the lowest common denominator, not the divisor..
anonymous
  • anonymous
100= 2*2 * 5*5 220= 2*2 * 5 * 11 Sorry I meant denominator
anonymous
  • anonymous
oh ok, i was getting a bit confused fro a second,
anonymous
  • anonymous
So again, both of our numbers have 2 2's, and one 5.
anonymous
  • anonymous
But one has an extra 5, and the other has an 11.
anonymous
  • anonymous
Do you see that?
anonymous
  • anonymous
yep i do!
anonymous
  • anonymous
Ok, so we have to make them the same
anonymous
  • anonymous
So we need to multiply 100 times 11, and 220 by 5 and they will have the same factors and therefore be the same number. And that number is our LCD.
anonymous
  • anonymous
oh ok!
anonymous
  • anonymous
So what is 5 * 220, and 100 * 11?
anonymous
  • anonymous
1100
anonymous
  • anonymous
yep. Now lets have you try it with either another problem you have, or my earlier example
anonymous
  • anonymous
ok lets see, how about, 95 and 100
anonymous
  • anonymous
Ok, so first factor them like we did before, 100 is easy since we already had that one the last time.
anonymous
  • anonymous
yep and its 10x10
anonymous
  • anonymous
No, you can factor that further remember?
anonymous
  • anonymous
10 is 5*2, so 100 is 5*2 * 5*2
anonymous
  • anonymous
oh yea sorry, i am so sorry i apparently have lack of memory
anonymous
  • anonymous
anyways, do go on...
anonymous
  • anonymous
Ok, so factor 95
anonymous
  • anonymous
ok 5x19 is one i know
anonymous
  • anonymous
but i cant think of any others
anonymous
  • anonymous
That's good. There are no others.
anonymous
  • anonymous
oh ok
anonymous
  • anonymous
So list the factors of 100, and the factors of 95 side by side and see which ones they have in common and which ones they do not.
anonymous
  • anonymous
ok so, 100: 5x2 5x2 and for 95: 5x19 so the all have fives
anonymous
  • anonymous
Ok, which ones do they not have in common?
anonymous
  • anonymous
19 and 2
anonymous
  • anonymous
Ok, specifically if we wanted to make them the same, what would we need to multiply by 100
anonymous
  • anonymous
not really sure....
anonymous
  • anonymous
100 has all the ones 95 has except?
anonymous
  • anonymous
19
anonymous
  • anonymous
Good. And 95 has all the ones 100 has except?
anonymous
  • anonymous
2
anonymous
  • anonymous
Close. It's actually two 2's and a 5. You have to count how many each one has.
anonymous
  • anonymous
oh ok so with that how do you make them the same?
anonymous
  • anonymous
Well you multiply the 100 by the ones it's missing (19) and the 95 by the ones it's missing (2*2*5)
anonymous
  • anonymous
And they should be the same.
anonymous
  • anonymous
and it would equal to 1900
anonymous
  • anonymous
100 * 19 = 1900, what about 95*2*2*5?
anonymous
  • anonymous
it equals the same, 1900
anonymous
  • anonymous
Yep, that's your LCD
anonymous
  • anonymous
Ok try another one on your own.
anonymous
  • anonymous
i will! thanks for all your help!!
anonymous
  • anonymous
Any time =)
anonymous
  • anonymous
wow i just did one on my own and i got it right, thank you for helping me understand!
anonymous
  • anonymous
Very welcome! =)
anonymous
  • anonymous
but i might need help on something else, if you have the time
anonymous
  • anonymous
Oh, when you can, go ahead and give me a medal, that's how the site determines whether or not the question is answered.
anonymous
  • anonymous
Of course, just start a new question and I'll take a look.
anonymous
  • anonymous
ok, i have these problems where im supposed to change a percent that is a mixed number into a fraction (in lowest terms) and the book gives me no help on how to do it
anonymous
  • anonymous
Ok, well start by turning the mixed number into a fraction.
anonymous
  • anonymous
for example, 5 3/8 percent into a fraction
anonymous
  • anonymous
Right, so start by turning the 5 3/8% into a improper fractional percentage
anonymous
  • anonymous
Basically ignore the percent for now.
anonymous
  • anonymous
ok hold up
anonymous
  • anonymous
dont you multiplie the 5 by 3 then add 8, or am i getting this mixed up
anonymous
  • anonymous
dont you do this: 5x3+8 then keep eight as your denominater
anonymous
  • anonymous
No, for improper fractions, you need to rewrite 5 as \(\frac{x}{8}\)
anonymous
  • anonymous
Then add it to the 3
anonymous
  • anonymous
sorry, i dont know what that is
anonymous
  • anonymous
5 and 3/8 \[= 5 + \frac{3}{8}\]\[ = \frac{5}{1} + \frac{3}{8}\] \[= \frac{5}{1} * 1 + \frac{3}{8}\] \[= \frac{5}{1}*\frac{8}{8} + \frac{3}{8}\] \[= \frac{40}{8} + \frac{3}{8}\] \[= \frac{43}{8}\]
anonymous
  • anonymous
ok, i kind of get it but kind of dont, if that makes any sense
anonymous
  • anonymous
like where did the one and the eight come from>
anonymous
  • anonymous
Well, you can always multiply 1 times something and get the same thing right?
anonymous
  • anonymous
right...
anonymous
  • anonymous
\[\frac{5}{1} = \frac{5}{1}*1\]
anonymous
  • anonymous
oh ok....
anonymous
  • anonymous
And any number over itself is 1 right?
anonymous
  • anonymous
right
anonymous
  • anonymous
\[\frac{8}{8} = 1 \implies \frac{5}{1}= \frac{5}{1}*1 = \frac{5}{1}*\frac{8}{8} = \frac{40}{8}\] This is just a very long way to say that \[5 = \frac{40}{8}\]
anonymous
  • anonymous
ok now it makes sense.... so ow that we have the 40/8 what do we do with it?
anonymous
  • anonymous
You could also answer that by just taking the denominator and multiplying it by the whole number part.
anonymous
  • anonymous
So then we add it to the fractional part.
anonymous
  • anonymous
So 5 and 3/8 as a fraction is 40/8 + 3/8
anonymous
  • anonymous
Take the denominator. Multiply it by the whole number. Then add that to the numerator of the fractional part. That's your improper fraction.
anonymous
  • anonymous
43/8...?
anonymous
  • anonymous
Yep. So 43/8 %
anonymous
  • anonymous
But we want that as just a fraction, not a percent.
anonymous
  • anonymous
right...
anonymous
  • anonymous
So to turn a percent into fraction a we just multiply the denominator by 100.
anonymous
  • anonymous
yep and that would be 800?? because you multiply 8 x 100= 800
anonymous
  • anonymous
Yep.
anonymous
  • anonymous
So 5 and 3/8 % = 43/800
anonymous
  • anonymous
oh ok..
anonymous
  • anonymous
So now you try one.
anonymous
  • anonymous
ok, and i will let you know if i get it right
anonymous
  • anonymous
ok
anonymous
  • anonymous
ok, heres my problem: 8 4/5 change it into a percent: i got 44/5 then multiplied it by 100 and got 44/100... is that correct?
anonymous
  • anonymous
No. 5 * 100 = 500, not 100.
anonymous
  • anonymous
thats what i ment sorry
anonymous
  • anonymous
Then yes, 44/500 is correct.
anonymous
  • anonymous
yay! thanks! and im sure i will have more questions, so when i do, ill just ask!
anonymous
  • anonymous
ok
anonymous
  • anonymous
how do i give you a medal?
anonymous
  • anonymous
ok, i have another question.....
anonymous
  • anonymous
nevermind!
anonymous
  • anonymous
Sorry, I had class. To give a medal you click the give medal button. next to any of my posts..

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