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# If the LCM of A and B is 72 and their HCF is 6, what is the

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Intern
Joined: 09 Feb 2012
Posts: 47

Kudos [?]: 64 [0], given: 14

If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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20 Aug 2012, 12:52
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Question Stats:

88% (00:13) correct 13% (00:00) wrong based on 12 sessions

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If the LCM of A and B is 72 and their HCF is 6, what is the product of A & B?

Thanks guys!

[Reveal] Spoiler:
OA: 432

Kudos [?]: 64 [0], given: 14

Math Expert
Joined: 02 Sep 2009
Posts: 41884

Kudos [?]: 129248 [1], given: 12196

Re: If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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20 Aug 2012, 12:57
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Expert's post
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NYC5648 wrote:
If the LCM of A and B is 72 and their HCF is 6, what is the product of A & B?

Thanks guys!

[Reveal] Spoiler:
OA: 432

The most important property of LCM (the least common multiple) and GCD (the greatest common divisors) is: for any positive integers $$x$$ and $$y$$, $$x*y=GCD(x,y)*LCM(x,y)$$, so AB=72*6=432.

Questions to practice:
if-x-and-y-are-positive-integers-is-xy-a-multiple-of-102540.html
if-x-and-y-are-positive-integers-what-is-the-value-of-xy-95872.html
if-the-least-common-multiple-of-integers-x-and-y-is-105745.html#p827452 (Karishma's post explaining this property)

Hope it helps.
_________________

Kudos [?]: 129248 [1], given: 12196

Senior Manager
Joined: 03 Sep 2012
Posts: 352

Kudos [?]: 230 [0], given: 35

Location: United States
Concentration: Healthcare, Strategy
GMAT 1: 730 Q48 V42
GPA: 3.88
WE: Medicine and Health (Health Care)
Re: If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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01 Oct 2012, 04:09
LCM of two numbers x GDF of the two numbers = Product of the two numbers ...

Therefore Product of A and B = 432 ...
_________________

"When you want to succeed as bad as you want to breathe, then you’ll be successful.” - Eric Thomas

Kudos [?]: 230 [0], given: 35

Manager
Joined: 16 Feb 2012
Posts: 220

Kudos [?]: 410 [0], given: 121

Concentration: Finance, Economics
Re: If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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15 Feb 2013, 08:21
Example:
You have two numbers x=8 and y=12.
LCM of x,y = 24
GCF of x,y = 4

(LCM of x and y) X (GCF of x and y) = XY
24 X 4 = 8 X 12
96 = 96
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Kudos [?]: 410 [0], given: 121

Intern
Joined: 31 Oct 2012
Posts: 13

Kudos [?]: [0], given: 19

Re: If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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15 Feb 2013, 09:14
Product A*B= lcm*hcf(gcd)= 72*6= 423

Kudos [?]: [0], given: 19

MBA Section Director
Status: Back to work...
Affiliations: GMAT Club
Joined: 22 Feb 2012
Posts: 4713

Kudos [?]: 3715 [1], given: 2420

Location: India
City: Pune
GMAT 1: 680 Q49 V34
GPA: 3.4
Re: If the LCM of A and B is 72 and their HCF is 6, what is the [#permalink]

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15 Feb 2013, 09:49
1
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Expert's post
Try to understand why is so.

take two numbers a and b

The prime factorization of those numbers is

a= d,d,e,r
b=d,e,g,h,i

HCF of a and b = d,e
LCM of a and b = d,e,d,r,g,h,i
Product of HCF and LCM = d.e.d.e.d.r.g.h.i ---------> d^3.e^2.r.g.h.i
Product of Numbers = d.d.e.r.d.e.g.h.i --------------> d^3.e^2.r.g.h.i

in my opinion it is better to understand any theorem/rule than to remember it.

Hope it clears!

Regards,

Abhijit.
_________________

Kudos [?]: 3715 [1], given: 2420

Re: If the LCM of A and B is 72 and their HCF is 6, what is the   [#permalink] 15 Feb 2013, 09:49
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