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Finding the number of unique factors | Explained in a 2-minutes video

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Experts' Global Representative
Joined: 19 Feb 2010
Posts: 235
Finding the number of unique factors | Explained in a 2-minutes video  [#permalink]

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23 Feb 2018, 17:56
Dear All,

Hope this finds you well.

Here is a short video for finding the number of unique factors of any number. The concept explained will help you solve questions such as the following in less than a minute.

Q. How many unique positive integers are factors of 20^10?

Hope this helps.

All the best!
Experts' Global Team
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Joined: 15 Sep 2017
Posts: 23
GMAT 1: 750 Q50 V42
GPA: 3.5
Re: Finding the number of unique factors | Explained in a 2-minutes video  [#permalink]

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24 Feb 2018, 12:22
Nice Video!

I'd like to just to add something to this topic:

One way the test can trick you is by not showing the primes behind the number.
For example (easy one):
399 is 133 x 3.
If you do (1+1) x (1+1), you get 4 factors, but actually 399 is 19 x 7 x 2 and it has (1+1) x (1+1) x (1+1) = 8 factors

Additionally, if the question asks you the number of factors of x = a^3 x b^4 x c^5, you can not assume that it is (3+1) x (4+1) x (5+1) = 120, as it could very well be that a = b = c and, therefore, x = a^12 and the number of factors is (12+1) = 13
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Experts' Global Representative
Joined: 19 Feb 2010
Posts: 235
Re: Finding the number of unique factors | Explained in a 2-minutes video  [#permalink]

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24 Feb 2018, 12:33

Yes, the bases involved need to be all different and prime.

These aspects have been covered at 00:20 and 01:20 In the video.

Thanks a ton for your contribution.

All the best!
Experts' Global Team

Sent from my SM-N950F using GMAT Club Forum mobile app
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Re: Finding the number of unique factors | Explained in a 2-minutes video   [#permalink] 24 Feb 2018, 12:33
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