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# Here is my collection of Quant questions from the 4GMAT.com

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Manager
Joined: 25 Apr 2006
Posts: 50

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Here is my collection of Quant questions from the 4GMAT.com [#permalink]

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14 Sep 2006, 20:11
Here is my collection of Quant questions from the 4GMAT.com website.
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4GMATSampleQuants.doc [285.5 KiB]

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Director
Joined: 14 Jan 2007
Posts: 775

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28 Mar 2007, 04:53
Thanks for posting this precious doc.
Keep posting good stuff.

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Senior Manager
Joined: 20 Feb 2007
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28 Mar 2007, 06:20
Quote:
How many zeros will be there in the value of 25!?

A. 25
B. 8
C. 6
D. 5
E. 2

The correct choice is (C) and the correct answer is 6.
25! is factorial 25 whose value = 25*24*23*22*â€¦..*1

When a number that has 5 as its factor is multiplied by another number that has 2 as its factor, the result will have â€˜0â€™ in its units digit.

In 25!, the numbers that have 5 as their factor are 5, 10, 15, 20, and 25. 25 is the square of 5 and hence has two 5â€™s in it.

Therefore, 25! contains in it 6 fives.
There are more than 6 even numbers in 25!. Hence, the limiting factor is the number of 5s.

And hence, the number 25! will have 6 zeroes in it.

Here is one question from this document and I found its answer wrong there.

25! = 1.551121 Ã— 10^(25)

How can it say that the number 25! will have 6 zeroes in it.

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Senior Manager
Joined: 20 Feb 2007
Posts: 256

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28 Mar 2007, 06:21
Quote:
How many zeros will be there in the value of 25!?

A. 25
B. 8
C. 6
D. 5
E. 2

The correct choice is (C) and the correct answer is 6.
25! is factorial 25 whose value = 25*24*23*22*â€¦..*1

When a number that has 5 as its factor is multiplied by another number that has 2 as its factor, the result will have â€˜0â€™ in its units digit.

In 25!, the numbers that have 5 as their factor are 5, 10, 15, 20, and 25. 25 is the square of 5 and hence has two 5â€™s in it.

Therefore, 25! contains in it 6 fives.
There are more than 6 even numbers in 25!. Hence, the limiting factor is the number of 5s.

And hence, the number 25! will have 6 zeroes in it.

Here is one question from this document and I found its answer wrong there.

25! = 1.551121 Ã— 10^(25) means 25 zeros in it.

Then how can it say that the number 25! will have 6 zeroes in it?

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Senior Manager
Joined: 20 Feb 2007
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28 Mar 2007, 06:32
OR

25! = 1.551121 * 10^(25) = 1551121 * 10^(19)

Any help???

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Intern
Joined: 18 Mar 2007
Posts: 1

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28 Mar 2007, 23:01
Hi Summer3,

The exact value is:

15511210043330985984000000.

You are adding zero's after rounding off.

Thanks a lot yessuresh for the quant problems.

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Director
Joined: 13 Dec 2006
Posts: 506

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Location: Indonesia

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28 Mar 2007, 23:50
Good posting suresh, Thanks a lot

regards,

Amardeep

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Senior Manager
Joined: 20 Feb 2007
Posts: 256

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29 Mar 2007, 02:58
I did google to get the value of 25!

Hmmm.....so google is here to blame

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Manager
Joined: 28 Aug 2012
Posts: 53

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Concentration: Operations, Marketing
GMAT 1: 510 Q36 V25
GPA: 4
WE: Information Technology (Other)
Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink]

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22 Mar 2013, 08:20
25! contains 25/5+25/5^2 = 5+1 = 6

Hope this helps

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Re: Here is my collection of Quant questions from the 4GMAT.com   [#permalink] 22 Mar 2013, 08:20
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