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# If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer,

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If k is an integer [#permalink]

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12 Nov 2010, 20:47
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If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12
[Reveal] Spoiler: OA

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Re: If k is an integer [#permalink]

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12 Nov 2010, 22:03
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monirjewel wrote:
If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12

Given: $$0.0025*0.025*0.00025*10^k=integer$$

There are 4 decimal places after zero in 0.0025, 3 decimal places after zero in 0.025 and 5 decimal places after zero in 0.00025 so in order the product to be an integer k must be at least 4+3+5=12 to convert all these fractions into the integers, in this case: $$0.0025*0.025*0.00025*10^{12}=25*25*25=integer$$

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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18 Oct 2015, 12:12
1
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Bunuel wrote:
If k is an integer and (0.0025)(0.025)(0.00025) × 10k is an integer, what is the least possible value of k?

(A) −12
(B) −6
(C) 0
(D) 6
(E) 12

Kudos for a correct solution.

It should be 10^k, not 10k

If so, Ans: E

(0.0025)(0.025)(0.00025) × 10^k = 10^k/(2^6*10^6).

=> k=6+6=12

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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18 Oct 2015, 20:43
2
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Bunuel wrote:
If k is an integer and (0.0025)(0.025)(0.00025) × 10k is an integer, what is the least possible value of k?

(A) −12
(B) −6
(C) 0
(D) 6
(E) 12

Kudos for a correct solution.

I too agree that it should be 10^k

and then answer would be K = 4 + 3 + 5 = 12, choice E

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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20 Oct 2015, 09:41
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(0.0025)(0.025)(0.00025) × 10k
$$(25*10^-^4*25*10^-^3*25*10^-^5)*10^k$$
$$(25*10^-^1^2)*10^k$$

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Re: If k is an integer [#permalink]

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27 Oct 2015, 03:35
1
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Dear Bunuel

I'm quite surprised with this math. If i'm not wrong, this is the same question [PS No.67] of OG 2016 which is among one of the 25% new questions. If it is a newly retired GMAT question, then how it appeared in forum in 2010?

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Re: If k is an integer [#permalink]

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27 Oct 2015, 04:29
1
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Expert's post
monirjewel wrote:
If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12

(.0025)(.025)(.00025)10^k = Integer

{25*10^(-4)}{25*10^(-3)}{25*10^(-5)}×10^k = Integer

(25^3)*10^(k-12) = Integer

I.e. (k-12) = Integer
I.e. Min (k-12)=0
I.e. (k)min = 12

Ans: Option E
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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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11 Dec 2015, 11:12
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since 25 to the power any integer will always yield last digit as 5 and not yield any 0, k is just summation of number of places we need to move the decimal point to get each individual number to be an integer i.e. 4+3+5=12
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If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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25 Dec 2016, 08:35
NoHalfMeasures wrote:
since 25 to the power any integer will always yield last digit as 5 and not yield any 0, k is just summation of number of places we need to move the decimal point to get each individual number to be an integer i.e. 4+3+5=12

Could you elaborate on this a little more? Specifically, this was my line of thought when answering this question. What scenario when multiplying decimals with same/different digits to 10^k would you get away with no moving the decimal over making each one an individual integer.

For example, the scenario where you would have (.005)(.002)*10^k you would need to move the decimal to make both integers. Can you extend what you're saying to, (any decimal)x(any decimal)*10^k, you have to make all decimals multiplied together integers?

Only scenario I can think of where you wouldn't have to is if one number isn't a decimal, for example (30)(.2)*10^k, k = 0 for it to be an integer..

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If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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03 Mar 2017, 17:59
1
KUDOS
Bunuel wrote:
monirjewel wrote:
If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12

Given: $$0.0025*0.025*0.00025*10^k=integer$$

There are 4 decimal places after zero in 0.0025, 3 decimal places after zero in 0.025 and 5 decimal places after zero in 0.00025 so in order the product to be an integer k must be at least 4+3+5=12 to convert all these fractions into the integers, in this case: $$0.0025*0.025*0.00025*10^{12}=25*25*25=integer$$

Hi. Can you please explain why it's not 10^-12? I understand how you get to 12, but have issues with how to know if it should be negative or positive.

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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04 Mar 2017, 01:15
mhill5446 wrote:
Bunuel wrote:
monirjewel wrote:
If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12

Given: $$0.0025*0.025*0.00025*10^k=integer$$

There are 4 decimal places after zero in 0.0025, 3 decimal places after zero in 0.025 and 5 decimal places after zero in 0.00025 so in order the product to be an integer k must be at least 4+3+5=12 to convert all these fractions into the integers, in this case: $$0.0025*0.025*0.00025*10^{12}=25*25*25=integer$$

Hi. Can you please explain why it's not 10^-12? I understand how you get to 12, but have issues with how to know if it should be negative or positive.

10^(-12) = 1/10^12

It's not 10^(-12) because if you substitute this value there you won't get an integer.

You can check easier example: 0.12*10^(-2) = 0.12*1/10^2=0.0012 but 0.12*10^2 = 12.
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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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07 Jul 2017, 07:04
I think this is bad or very hard question

because 25*25* 25 have no ending in 10, we can infer that all of factor must be interger, and E is the answer
what happen if

0. 25*0.20.10^k

so this is hard.

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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22 Jul 2017, 07:26
caution, pls,

the value is
25*25*25*10^-12*10^k

because the digit number of 25^3 is 5 not 0, we can infer that k=12
but if
the value is
25*20
then the problem is different.

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer, [#permalink]

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08 Dec 2017, 10:25
monirjewel wrote:
If k is an integer and (.0025)(.025)(.00025)10^k is an integer, what is the least possible value of K?

(A) -12
(B) -6
(C) 0
(D) 6
(E) 12

We are given the expression:

0.0025 x 0.025 x 0.00025 x 10^k = integer

To determine the least possible value of k, we want to use our rules of multiplication with decimals. When multiplying decimals, the final product has an equal number of decimal places to the decimal places of the numbers being multiplied. Let’s start by counting the number of decimal places.

0.0025 has 4 decimal places

0.025 has 3 decimal places

0.00025 has 5 decimal places

Thus, the result of 0.0025 x 0.025 x 0.00025 will have 12 decimal places.

In order for 0.0025 x 0.025 x 0.00025 x 10^k = integer, k would have to be at least 12, since 10^12 times any number with 12 decimal places would move the decimal point of that number 12 places to the right, making it an integer.

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Re: If k is an integer and (0.0025)(0.025)(0.00025) × 10^k is an integer,   [#permalink] 08 Dec 2017, 10:25
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