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# if r represents the number of unique prime factors in the products of

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Intern
Joined: 24 Nov 2018
Posts: 19
Location: India
if r represents the number of unique prime factors in the products of  [#permalink]

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10 Mar 2019, 07:13
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if r represents the number of unique prime factors in the products of positive integers S and T, what is the value of r^2- r?

1) The lCM of S and T is 120
2) The HCF of S and T is 6
Director
Joined: 18 Jul 2018
Posts: 760
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: if r represents the number of unique prime factors in the products of  [#permalink]

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10 Mar 2019, 09:44
Each statement is individually Insufficient.

Combining both. The product of two numbers, S*T = LCM*HCF = 120*6 = 720 = $$2^4*3^2*5^1$$
Unique prime factors are 2,3 and 5.
therefore r = 3.
$$r^2-r = 3^2-3 = 6$$

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Joined: 15 Dec 2018
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Re: if r represents the number of unique prime factors in the products of  [#permalink]

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10 Mar 2019, 09:58
IMO C

Using principle as below

Product of 2 numbers = GCFXLCM

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Re: if r represents the number of unique prime factors in the products of   [#permalink] 10 Mar 2019, 09:58
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