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

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Manager
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Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post 14 Sep 2006, 19:11
Here is my collection of Quant questions from the 4GMAT.com website.
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Director
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 [#permalink] New post 28 Mar 2007, 03:53
Thanks for posting this precious doc.
Keep posting good stuff.
Senior Manager
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 [#permalink] New post 28 Mar 2007, 05:20
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.
Senior Manager
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 [#permalink] New post 28 Mar 2007, 05:21
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?
:?
Senior Manager
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 [#permalink] New post 28 Mar 2007, 05:32
OR

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

Any help???
Intern
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 [#permalink] New post 28 Mar 2007, 22:01
Hi Summer3,

The exact value is:

15511210043330985984000000.

You are adding zero's after rounding off.

Thanks a lot yessuresh for the quant problems.
Director
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 [#permalink] New post 28 Mar 2007, 22:50
Good posting suresh, Thanks a lot

regards,

Amardeep
Senior Manager
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 [#permalink] New post 29 Mar 2007, 01:58
I did google to get the value of 25!

Hmmm.....so google is here to blame :)
Manager
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Joined: 28 Aug 2012
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Concentration: Operations, Marketing
GMAT 1: 510 Q36 V25
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Re: Here is my collection of Quant questions from the 4GMAT.com [#permalink] New post 22 Mar 2013, 07:20
25! contains 25/5+25/5^2 = 5+1 = 6

Hope this helps :)
Re: Here is my collection of Quant questions from the 4GMAT.com   [#permalink] 22 Mar 2013, 07:20
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Here is my collection of Quant questions from the 4GMAT.com

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