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Math: Number Theory

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Re: Math: Number Theory [#permalink]

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New post 27 Oct 2016, 02:30
• Any positive divisor of n is a product of prime divisors of n raised to some power.



pls someone explain with example
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Re: Math: Number Theory [#permalink]

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New post 27 Oct 2016, 03:59
sanaexam wrote:
• Any positive divisor of n is a product of prime divisors of n raised to some power.



pls someone explain with example


For example, say n = 72. Consider it's factor 36 --> \(36 = 2^2*3^2\) --> 36 = product of prime divisors of n raised to some power.
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Re: Math: Number Theory [#permalink]

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New post 23 May 2017, 16:47
Bunuel wrote:
NUMBER THEORY

Fractions (also known as rational numbers) can be written as terminating (ending) or repeating decimals (such as 0.5, 0.76, or 0.333333....).

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


0.333333... looks like a recurring decimal and is not a rational number. This can be better modified as 0.33333 etc so it is less confusing in my opinion.
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Re: Math: Number Theory [#permalink]

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New post 24 May 2017, 04:02
workout wrote:
Bunuel wrote:
NUMBER THEORY

Fractions (also known as rational numbers) can be written as terminating (ending) or repeating decimals (such as 0.5, 0.76, or 0.333333....).

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


0.333333... looks like a recurring decimal and is not a rational number. This can be better modified as 0.33333 etc so it is less confusing in my opinion.


0.333333... IS a rational number because it equals to the ratio of two integers: 1/3 = 0.3333......
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Re: Math: Number Theory [#permalink]

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New post 28 Feb 2018, 18:18
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Adding Few Formulas

Sum of First "n" natural nos = n(n+1)/2
Sum of First "n" ODD natural nos = n^2
Sum of First "n" EVEN natural nos = n (n+1)
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Re: Math: Number Theory [#permalink]

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New post 27 Mar 2018, 05:40
Hi Bunuel
The topic doesn’t touch up on LCM and HCF for fractions..

LCM( (a/b) , (c/d) ) = LCM(a,c)/HCF(b,d))

HCF( (a/b) , (c/d) ) = HCF(a,c)/LCM(b,d)

Please add if tested on GMAT.

Question from where I started to look for the theory:
https://gmatclub.com/forum/what-is-the- ... ml#p818818
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Math: Number Theory [#permalink]

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New post 04 May 2018, 04:45
Bunuel niks18 gmatbusters pushpitkc VeritasPrepKarishma

I have a small query regarding rounding:

How do I interpret nearest ten, nearest hundred etc in

1234.1234

on both LHS and RHS of decimal?
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Re: Math: Number Theory [#permalink]

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New post 04 May 2018, 06:03
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Hii

You have asked regarding rounding to nearest tens, hundred for 1234.1234 on both LHS and RHS of decimal.

First of all , Lets know what does the place signify:
we denote the digits as units, tens, hundreds, thousands before decimal and tenth, hundredth after decimal. see the sketch
Attachment:
gmatbusters3.jpg
gmatbusters3.jpg [ 27.32 KiB | Viewed 358 times ]


Rounding
Simplifying a number to a certain place value. Drop the extra decimal places, and if the first dropped digit is 5 or greater, round up the last digit that you keep. If the first dropped digit is 4 or smaller, round down (keep the same) the last digit that you keep.

It means if we round 47 to nearest ten = 50
whereas, 44 to nearest ten = 40

Now lets come to your question:
1234.1234
Rounding to nearest ten = 1230
Rounding to nearest hundred = 1200
Rounding to nearest tenth =1234.1
Rounding to nearest hundredth= 1234.12

I hope it is clear now. Fell free to tag again.


adkikani wrote:

I have a small query regarding rounding:

How do I interpret nearest ten, nearest hundred etc in

1234.1234

on both LHS and RHS of decimal?

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Math: Number Theory [#permalink]

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New post 04 May 2018, 06:56
gmatbusters

Thanks for the pic ;) , that made me wonder if the difference in position of tens on LHS and RHS
is because of raising base of 10 to exponents say 0,1 and -1. Is this how we arrive at
PLACE VALUES for a number?

Spoiler: ::
Sorry, coming from engineering bakground, am still
not able to erase why aspects of logic :lol:

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Re: Math: Number Theory [#permalink]

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New post 04 May 2018, 07:03
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yes you got it right
Attachment:
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adkikani wrote:
gmatbusters

Thanks for the pic ;) , that made me wonder if the difference in position of tens on LHS and RHS
is because of raising base of 10 to exponents say 0,1 and -1. Is this how we arrive at
PLACE VALUES for a number?

Spoiler: ::
Sorry, coming from engineering bakground, am still
not able to erase why aspects of logic :lol:

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Re: Math: Number Theory   [#permalink] 04 May 2018, 07:03
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