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What is the tens digit of the positive integer r?

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Guest
 Post subject: What is the tens digit of the positive integer r?
 Post Posted: Tue Jul 01, 2008 9:48 pm 
What is the tens digit of the positive integer r?

1. The tens digit of r/10 is 3.
2. The hundreds digit of 10r is 6.

Data Suff.-Gmat Prep 1

How can I go about solving this problem?

Your input is appreciated....
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Guest
 Post subject: Re: What is the tens digit of the positive integer r?
 Post Posted: Wed Jul 02, 2008 12:34 am 
[quote="Anonymous"]What is the tens digit of the positive integer r?

1. The tens digit of r/10 is 3.
2. The hundreds digit of 10r is 6.

B

let the number be xxxx6x
stem 2 says
The hundreds digit of 10r is 6.
thus my new number will xxxx6xx
so unit digit has to be 6 in original number

from stem 1
original number xxxx6x
divide by 10 gives 3 in tens
xxx36
hence no information can be inferred
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Guest
 Post subject:
 Post Posted: Wed Jul 02, 2008 11:56 am 
Hi instructors,
Could you please see if I have a good understanding of the problem from what I have written below? Your input is greatly appreciated....

Is statement 1 insuf. because you are dividing by a power of 10 and when you divide by a power the number of zeros decreases, since here you are dealing with a whole number and no decimal. So, the tens place becomes the units place and therefore the answer is insuf.

In statement 2 you are multiplying by a power of 10, in this case, you are adding zeros, so the 6 now becomes the tens place as opposed to the hundreds place.

The answer is B.


Thanks
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RonPurewal
 Post subject:
 Post Posted: Sat Jul 12, 2008 4:35 am 
Offline
ManhattanGMAT Staff


Posts: 6765
Anonymous wrote:
Hi instructors,
Could you please see if I have a good understanding of the problem from what I have written below? Your input is greatly appreciated....

Is statement 1 insuf. because you are dividing by a power of 10 and when you divide by a power the number of zeros decreases, since here you are dealing with a whole number and no decimal. So, the tens place becomes the units place and therefore the answer is insuf.

In statement 2 you are multiplying by a power of 10, in this case, you are adding zeros, so the 6 now becomes the tens place as opposed to the hundreds place.

The answer is B.


Thanks


correct.

interestingly, the fact that r is an integer is completely irrelevant to the solution; the properties of digits of non-integers are exactly the same as the properties of digits of integers.
there are some special facts about integers, though, because all of their decimal places are 0 (i.e., there's nothing after the decimal point of an integer, except 0000....). for instance, if x is an integer, then both the units and tens digits of 100x must be 0. etc.
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birgiolasj
 Post subject: Re: What is the tens digit of the positive integer r?
 Post Posted: Tue May 17, 2011 10:20 pm 
Offline
Forum Guests


Posts: 1
Given: r is an int > 0
Question: ten's digit of r?
---
1: ten's digit of r/10 is 3
r/10 = 3_
r=3_ * 10
r=3_0
_ is the 10's digit -> not sufficient

---
2: hundreds digit of 10r is 6
6__ = 10r
6_._=r
6 is the 10's digit -> sufficient

B
-----------------
Alternatively,
1: ten's digit of r/10 is 3
number r divided by 10 is thirty something
so, r is three hundred something
don't have ten's -> insufficient

2: hundreds digit of 10r is 6
number r times 10 is 6 hundred something
so, r must be sixty something
got ten's -> sufficient

---
-Justas
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RonPurewal
 Post subject: Re: What is the tens digit of the positive integer r?
 Post Posted: Sat May 21, 2011 4:24 am 
Offline
ManhattanGMAT Staff


Posts: 6765
that's the idea, yes.
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