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

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yessuresh
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Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   14 Sep 2006, 20:11
Here is my collection of Quant questions from the 4GMAT.com website.



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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   28 Mar 2007, 04:53
Thanks for posting this precious doc.
Keep posting good stuff.
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Summer3
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   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.
Explanatory Answer
25! is factorial 25 whose value = 25*24*23*22*…..*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 ‘0’ 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 5’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 × 10^(25)

How can it say that the number 25! will have 6 zeroes in it.
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Summer3
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   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.
Explanatory Answer
25! is factorial 25 whose value = 25*24*23*22*…..*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 ‘0’ 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 5’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 × 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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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   28 Mar 2007, 06:32
OR

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

Any help???
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milmerry
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   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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Amardeep Sharma
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   28 Mar 2007, 23:50
Good posting suresh, Thanks a lot

regards,

Amardeep
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Summer3
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   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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thinktank
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post   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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