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If a, b, c are positive integers what is the range of the five numbers

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If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13

Originally posted by surupab on 10 Apr 2016, 09:01.
Last edited by Bunuel on 10 Apr 2016, 09:41, edited 1 time in total.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 10 Apr 2016, 09:22
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surupab wrote:
if a,b,c are positive integers what is the range of the five numbers 0,10,a,b,c
(1) a+b+c< 13
(2) a<b<c<13


lets see the statements

(1) a+b+c< 13
let the sum be the max and one of the three a,b and c be the max possible
so a+b+c=12..
let a and b the min so that c is the max..
a=b=1, so c= 12-1-1=10..
Therefor ewhatever be the value of a, b and c .. range will remain 10
Suff

(2) a<b<c<13
we just know that a, b and c are distinct integers< 13 and >0..
so c could be anything from 3 to 10, then range will be 10..
if c=11, range = 11
if c=12, range =12..
different anserws
Insuff


A
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 11 Apr 2016, 02:50
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If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13

There are 3 variables (a,b and c) in the original condition. In order to match the number of variables to the number of equations, we need 3 equations. Since the condition 1) and the condition 2) each has 1 equation, we need 1 more equation. Therefore, there is high chance that E is the correct answer. If we use the condition 1) and the condition 2) at the same time, we get a=1, b=2 and c=9. The numbers are unique and the range becomes 10-0=10. Hence, the conditions are sufficient. So the answer is C. However, this is one of the key questions involving integer and statistics. Hence, we have to apply the Common Mistake Type 4(A).
Looking at the condition 1) and 2) separately:

For the condition 1), even if a=b=1 and c=10, the range is still 10-0=10. So, the answer is unique and the condition is sufficient.
For the condition 2), when a=1, b=2 and c=9, range is 10-0=10. When a=1, b=2 and c=12, the range becomes 12-0=12. The answer is not unique and the condition is not sufficient. So the correct answer is A.
l For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 12 Apr 2016, 00:09
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surupab wrote:
If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13


Analyse it like this:

0, 10, a, b, c
a, b and c are positive integers so their minimum value is 1 and maximum could be anything.
There is already 0 in the list so it will be the minimum for the range.
Now we need to find the maximum for the range. That will depend on the values of a, b and c. If at least one of them is more than 10, the range will be more than 10 else it will be 10.

(1) a+b+c< 13
a, b and c are at least 1. Their sum is 12 or less. Assuming their sum is 12 (since we need the maximum value one of a, b and c can take), the maximum value one of them can take is 10 in which case other two will be 1 each.
So maximum of this set is 10 only.
Range = 10 - 0 = 10
Sufficient.

(2) a<b<c<13
c could be maximum 12, b maximum 11 and a maximum 10.
So maximum of this set could be anything from 10 to 12 and hence the range could be from 10 to 12.
Not sufficient.

Answer (A)
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 18 Jul 2016, 01:44
VeritasPrepKarishma wrote:
surupab wrote:
If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13


Analyse it like this:

0, 10, a, b, c
a, b and c are positive integers so their minimum value is 1 and maximum could be anything.
There is already 0 in the list so it will be the minimum for the range.
Now we need to find the maximum for the range. That will depend on the values of a, b and c. If at least one of them is more than 10, the range will be more than 10 else it will be 10.

(1) a+b+c< 13
a, b and c are at least 1. Their sum is 12 or less. Assuming their sum is 12 (since we need the maximum value one of a, b and c can take), the maximum value one of them can take is 10 in which case other two will be 1 each.
So maximum of this set is 10 only.
Range = 10 - 0 = 10
Sufficient.

(2) a<b<c<13
c could be maximum 12, b maximum 11 and a maximum 10.
So maximum of this set could be anything from 10 to 12 and hence the range could be from 10 to 12.
Not sufficient.

Answer (A)


Hi Karishma,

Can you please clarify why have we taken the sum as 12 in first case. I know that is the maximum that we can consider but the question is simply asking for a range and not the maximum range. If we take a+b+c = 11 then the values will differ.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 18 Jul 2016, 22:45
1
nishatfarhat87 wrote:
VeritasPrepKarishma wrote:
surupab wrote:
If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13


Analyse it like this:

0, 10, a, b, c
a, b and c are positive integers so their minimum value is 1 and maximum could be anything.
There is already 0 in the list so it will be the minimum for the range.
Now we need to find the maximum for the range. That will depend on the values of a, b and c. If at least one of them is more than 10, the range will be more than 10 else it will be 10.

(1) a+b+c< 13
a, b and c are at least 1. Their sum is 12 or less. Assuming their sum is 12 (since we need the maximum value one of a, b and c can take), the maximum value one of them can take is 10 in which case other two will be 1 each.
So maximum of this set is 10 only.
Range = 10 - 0 = 10
Sufficient.

(2) a<b<c<13
c could be maximum 12, b maximum 11 and a maximum 10.
So maximum of this set could be anything from 10 to 12 and hence the range could be from 10 to 12.
Not sufficient.

Answer (A)


Hi Karishma,

Can you please clarify why have we taken the sum as 12 in first case. I know that is the maximum that we can consider but the question is simply asking for a range and not the maximum range. If we take a+b+c = 11 then the values will differ.


We need the range of 0, 10, a, b, c
The smallest number here is 0. a, b and c are positive integers so they are at least 1. Hence the minimum value in this set will remain 0 only.
The largest number right now is 10. If one of a, b and c is greater than 10, it will increase the range. So we need to find the maximum value that any one of these can take. To take the maximum value, the sum of all 3 will also be maximum. The maximum sum is 12 and that is why we try to find the maximum value of a, b or c when the sum is 12.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 18 Jul 2016, 22:59
Hi Karishma,

Can you please clarify why have we taken the sum as 12 in first case. I know that is the maximum that we can consider but the question is simply asking for a range and not the maximum range. If we take a+b+c = 11 then the values will differ.[/quote]

We need the range of 0, 10, a, b, c
The smallest number here is 0. a, b and c are positive integers so they are at least 1. Hence the minimum value in this set will remain 0 only.
The largest number right now is 10. If one of a, b and c is greater than 10, it will increase the range. So we need to find the maximum value that any one of these can take. To take the maximum value, the sum of all 3 will also be maximum. The maximum sum is 12 and that is why we try to find the maximum value of a, b or c when the sum is 12.[/quote]

Thanks for your response but I think I didn't frame my question correctly so let me try again.

If a question asks us for Range do we automatically try for the possible maximum value one of them can ascertain instead of the actual value. For eg if a+b+c<13 so I calculate value based on the assumption that it will be max and hence a+b+c = 12 and not a+b+c=11 or 10.
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If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 19 Jul 2016, 04:34
nishatfarhat87 wrote:
Hi Karishma,

Can you please clarify why have we taken the sum as 12 in first case. I know that is the maximum that we can consider but the question is simply asking for a range and not the maximum range. If we take a+b+c = 11 then the values will differ.

We need the range of 0, 10, a, b, c
The smallest number here is 0. a, b and c are positive integers so they are at least 1. Hence the minimum value in this set will remain 0 only.
The largest number right now is 10. If one of a, b and c is greater than 10, it will increase the range. So we need to find the maximum value that any one of these can take. To take the maximum value, the sum of all 3 will also be maximum. The maximum sum is 12 and that is why we try to find the maximum value of a, b or c when the sum is 12.

Thanks for your response but I think I didn't frame my question correctly so let me try again.

If a question asks us for Range do we automatically try for the possible maximum value one of them can ascertain instead of the actual value. For eg if a+b+c<13 so I calculate value based on the assumption that it will be max and hence a+b+c = 12 and not a+b+c=11 or 10.


Since we need to determine if A is sufficient to get the answer , we are taking all the possibilities.

Let's see it like this

If you take a+b+c= 12 and we know that minimum value of any of these three variables is 1. => Say a=b=1 => c=10. Thus Range would be 10-0=10.
Now, say a+b+c=10(as you mentioned). in that case, say a=b=1 => c=8. but we already have 10 and 0 in the original list. => Range will still be 10-0=10, no matter what the value of a,b and c be.

Thus, Statement 1 is sufficient.

Where Statement 2 says a<b<c<13. In this case we can have c=12. It would change the range of the list to 12 instead of 10. Thus, it is insufficient.
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If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 19 Jul 2016, 22:01
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nishatfarhat87 wrote:
Hi Karishma,

Can you please clarify why have we taken the sum as 12 in first case. I know that is the maximum that we can consider but the question is simply asking for a range and not the maximum range. If we take a+b+c = 11 then the values will differ.

We need the range of 0, 10, a, b, c
The smallest number here is 0. a, b and c are positive integers so they are at least 1. Hence the minimum value in this set will remain 0 only.
The largest number right now is 10. If one of a, b and c is greater than 10, it will increase the range. So we need to find the maximum value that any one of these can take. To take the maximum value, the sum of all 3 will also be maximum. The maximum sum is 12 and that is why we try to find the maximum value of a, b or c when the sum is 12.


Thanks for your response but I think I didn't frame my question correctly so let me try again.

If a question asks us for Range do we automatically try for the possible maximum value one of them can ascertain instead of the actual value. For eg if a+b+c<13 so I calculate value based on the assumption that it will be max and hence a+b+c = 12 and not a+b+c=11 or 10.[/quote]

If we can get the actual value - great! But in this question, all we know is a + b + c < 13. We don't know the actual values of a, b and c. All we are trying to establish is that no matter what the actual values of these variables, under the given constraints, the range will stay at 10 only.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 29 Jul 2017, 03:50
VeritasPrepKarishma wrote:
surupab wrote:
If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13


Analyse it like this:

0, 10, a, b, c
a, b and c are positive integers so their minimum value is 1 and maximum could be anything.
There is already 0 in the list so it will be the minimum for the range.
Now we need to find the maximum for the range. That will depend on the values of a, b and c. If at least one of them is more than 10, the range will be more than 10 else it will be 10.

(1) a+b+c< 13
a, b and c are at least 1. Their sum is 12 or less. Assuming their sum is 12 (since we need the maximum value one of a, b and c can take), the maximum value one of them can take is 10 in which case other two will be 1 each.
So maximum of this set is 10 only.
Range = 10 - 0 = 10
Sufficient.

(2) a<b<c<13
c could be maximum 12, b maximum 11 and a maximum 10.
So maximum of this set could be anything from 10 to 12 and hence the range could be from 10 to 12.
Not sufficient.

Answer (A)


Hi Karishma,

A small query, in GMAT we can take same value (1 in this case) for different variables (in this case a,b) ? Got this confusion while doing this question.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 29 Jul 2017, 04:04
Yashkumar wrote:
VeritasPrepKarishma wrote:
surupab wrote:
If a, b, c are positive integers what is the range of the five numbers 0, 10, a, b, c

(1) a+b+c< 13
(2) a<b<c<13


Analyse it like this:

0, 10, a, b, c
a, b and c are positive integers so their minimum value is 1 and maximum could be anything.
There is already 0 in the list so it will be the minimum for the range.
Now we need to find the maximum for the range. That will depend on the values of a, b and c. If at least one of them is more than 10, the range will be more than 10 else it will be 10.

(1) a+b+c< 13
a, b and c are at least 1. Their sum is 12 or less. Assuming their sum is 12 (since we need the maximum value one of a, b and c can take), the maximum value one of them can take is 10 in which case other two will be 1 each.
So maximum of this set is 10 only.
Range = 10 - 0 = 10
Sufficient.

(2) a<b<c<13
c could be maximum 12, b maximum 11 and a maximum 10.
So maximum of this set could be anything from 10 to 12 and hence the range could be from 10 to 12.
Not sufficient.

Answer (A)


Hi Karishma,

A small query, in GMAT we can take same value (1 in this case) for different variables (in this case a,b) ? Got this confusion while doing this question.


Yes, unless it is explicitly stated otherwise, different variables CAN represent the same number.
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Re: If a, b, c are positive integers what is the range of the five numbers  [#permalink]

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New post 26 Mar 2018, 16:32
:( I somehow wrote down less than or equal to 13 on my scratch paper for a test exam, I was wondering how I got it wrong until i re-read the question
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Re: If a, b, c are positive integers what is the range of the five numbers &nbs [#permalink] 26 Mar 2018, 16:32
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