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qlx
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The sum of n consecutive positive integers is 45 24 Apr 2014, 03:08
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Bunuel
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Multiplication of the two digit numbers wx and cx, where w,x and c are unique non-zero digits, the product is a three digit number. What is w+c-x?
(1) The three digits of the product are all the same and different from w c and x.
(2) x and w+c are odd numbers.

(1) wx+cx=aaa (111, 222, ... 999=37*k) --> As x is the units digit in both numbers, a can be 1,4,6 or 9 (2,3,7 out because x^2 can not end with 2,3, or 7. 5 is out because in that case x also should be 5 and we know that x and a are distinct numbers).
1 is also out because 111=37*3 and we need 2 two digit numbers.
444=37*12 no good we need units digit to be the same.
666=37*18 no good we need units digit to be the same.
999=37*27 is the only possibility all digits are distinct except the unit digits of multiples.
Sufficient
(2) x and w+c are odd numbers.
Number of choices: 13 and 23 or 19 and 29 and w+c-x is the different even number.

Answer: A.

am I missing anything?
it does not say that w x and c are positive, does it?
w= 3, c= 2 and x= 7
37*27 = 999, here w+c -7 = -2

but we also can have
w= -3 and c= -2 and x= 7
-37*-27 = 999, here w+c - 7 = -12

Both of these sets satisfy both the conditions , hence I am getting E,

w, x and c are unique non-zero digits of the two digit numbers wx and cx means that w, x, and c are 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Hope it's clear.
Show more

Thank you for your reply
Sorry for the delayed post, but couldn't it be better if it was mentioned that w, c, x are non zero positive integers?

"w, x and c are unique non-zero digits of the two digit numbers wx and cx" - From this statement how can we deduce or assume that the 2 digit number cannot be negative ?


As of now one could argue wx = -37 and cx = -27 is also a possibility.
here I have taken w = -3 and x= 7 and c= -2

Hope you agree.

Thank you and appreciate your help.
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The sum of n consecutive positive integers is 45 24 Apr 2014, 03:14
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w, x and c are unique non-zero digits of the two digit numbers wx and cx means that w, x, and c are 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Hope it's clear.

Thank you for your reply
Sorry for the delayed post, but couldn't it be better if it was mentioned that w, c, x are non zero positive integers?

"w, x and c are unique non-zero digits of the two digit numbers wx and cx" - From this statement how can we deduce or assume that the 2 digit number cannot be negative ?


As of now one could argue wx = -37 and cx = -27 is also a possibility.
here I have taken w = -3 and x= 7 and c= -2

Hope you agree.

Thank you and appreciate your help.
Show more

Two-digit numbers wx means positive integer, where w is the tens digit and x is the units digit: 10, 11, 12, ..., 99.

Two-digit numbers -wx means negative integer, where w is the tens digit and x is the units digit: -10, -11, -12, ..., -99.
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The sum of n consecutive positive integers is 45 Updated on: 24 Apr 2014, 04:09
Originally posted by qlx on 24 Apr 2014, 03:44.
Last edited by qlx on 24 Apr 2014, 04:09, edited 1 time in total.
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Bunuel

Two-digit numbers wx means positive integer, where w is the tens digit and x is the units digit: 10, 11, 12, ..., 99.

Two-digit numbers -wx means negative integer, where w is the tens digit and x is the units digit: -10, -11, -12, ..., -99.

Show more

Thank you I finally got what you are saying.

I think a variable representing an integer can be positive or negative ( or zero) , a variable without a minus sign does not mean that the variable is positive does it .

using the same logic
if a particular sum says

if a and b are integers what is b ?

1) a+b = 1
2) a= 2

From here can we say that a is positive ,because it is not -a ?
so a means = a is a positive integer
and -a means = a is a negative integer

In the same way when it says wx is a two digit integer , how can we say because it is not -wx hence wx is positive.
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The sum of n consecutive positive integers is 45 24 Apr 2014, 03:57
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qlx
Bunuel

Two-digit numbers wx means positive integer, where w is the tens digit and x is the units digit: 10, 11, 12, ..., 99.

Two-digit numbers -wx means negative integer, where w is the tens digit and x is the units digit: -10, -11, -12, ..., -99.


Thank you I finally got what you are saying.

I think a variable representing an integer can be positive or negative , a variable without a minus sign does not mean that the variable is positive does it .

using the same logic
if a particular sum says

if a and b are integers what is b ?

1) a+b = 1
2) a= 2

From here can we say that a is positive ,because it is not -a ?
so a means = a is a positive integer
and -a means = a is a negative integer

In the same way when it says wx is a two digit integer , how can we say because it is not -wx hence wx is positive.
Show more

a is an integer does not mean that a is positive but a is a digit means that a is positive: 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Sorry cannot explain any better.
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The sum of n consecutive positive integers is 45 24 Apr 2014, 04:27
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Bunuel
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Bunuel

Two-digit numbers wx means positive integer, where w is the tens digit and x is the units digit: 10, 11, 12, ..., 99.

Two-digit numbers -wx means negative integer, where w is the tens digit and x is the units digit: -10, -11, -12, ..., -99.


Thank you I finally got what you are saying.

I think a variable representing an integer can be positive or negative , a variable without a minus sign does not mean that the variable is positive does it .

using the same logic
if a particular sum says

if a and b are integers what is b ?

1) a+b = 1
2) a= 2

From here can we say that a is positive ,because it is not -a ?
so a means = a is a positive integer
and -a means = a is a negative integer

In the same way when it says wx is a two digit integer , how can we say because it is not -wx hence wx is positive.

a is an integer does not mean that a is positive but a is a digit means that a is positive: 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Sorry cannot explain any better.
Show more

Thank you for your explanation ,

So the terms " Integer" and " Digit " makes all the difference ?They do not mean the same thing, right?

Integer =both negative , positive or zero
Digit = only 0 or positive.

I thought ( -2) was a digit too! a negative digit? Can we not have a negative digit?

Or is the Digit term in GMAT only used for non negative integers.

I think this is important info in terms of Gmat.

Really appreciate your help.Thank you so much .
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The sum of n consecutive positive integers is 45 01 May 2014, 22:29
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qlx

So the terms " Integer" and " Digit " makes all the difference ?They do not mean the same thing, right?

Integer =both negative , positive or zero
Digit = only 0 or positive.

I thought ( -2) was a digit too! a negative digit? Can we not have a negative digit?

Or is the Digit term in GMAT only used for non negative integers.

I think this is important info in terms of Gmat.

Really appreciate your help.Thank you so much .
Show more

Responding to a pm: Here goes my honest opinion you asked for!

An integer can be positive, negative or 0.

A single digit, on the other hand always implies a positive single digit from 0 to 9.
Given ab where a and b are single digits, ab is a positive integer.

In the question, you have "Multiplication of the two digit numbers wx and cx, where w,x and c are unique non-zero digits, the product is a three digit number".
This implies that w, c and x are distinct digits from 1 to 9 and wx and cx are positive integers.

The author did not forget to mention "positive digits". He/she did not need to mention it because digits imply positive digits only.

Also, in case of confusion, you can always search on Google. Say, put "digit in Math" and check out the various write ups. If there are multiple usages, the net will tell you that too.
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The sum of n consecutive positive integers is 45 04 May 2014, 07:15
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Hi bunnel

8. If x and y are non-zero integers and |x| + |y| = 32, what is xy?
(1) -4x - 12y = 0
(2) |x| - |y| = 16

(1) x+3y=0 --> x and y have opposite signs --> either 4y=32 y=8 x=-3, xy=-24 OR -4y=32 y=-8 x=3 xy=24. The same answer. Sufficient..... how is x = -3, when y = 8?... isnt x=-3y??
(2) Multiple choices. Not sufficient.
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The sum of n consecutive positive integers is 45 04 May 2014, 07:47
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Hi bunnel

8. If x and y are non-zero integers and |x| + |y| = 32, what is xy?
(1) -4x - 12y = 0
(2) |x| - |y| = 16

(1) x+3y=0 --> x and y have opposite signs --> either 4y=32 y=8 x=-3, xy=-24 OR -4y=32 y=-8 x=3 xy=24. The same answer. Sufficient..... how is x = -3, when y = 8?... isnt x=-3y??
(2) Multiple choices. Not sufficient.
Show more

There was a typo. Correct solution is below:

If x and y are non-zero integers and |x| + |y| = 32, what is xy?

(1) \(-4x-12y=0\) --> \(x=-3y\) --> \(x\) and \(y\) have opposite signs.

So either: \(|x|=x\) and \(|y|=-y\) --> in this case \(|x|+|y|=x-y=-3y-y=-4y=32\): \(y=-8\), \(x=24\), \(xy=-24*8\);

OR: \(|x|=-x\) and \(|y|=y\) --> \(|x|+|y|=-x+y=3y+y=4y=32\) --> \(y=8\) and \(x=-24\) --> \(xy=-24*8\), the same answer.

Sufficient.

(2) \(|x| - |y| = 16\). Sum this one with th equations given in the stem --> \(2|x|=48\) --> \(|x|=24\), \(|y|=8\). \(xy=-24*8\) (x and y have opposite sign) or \(xy=24*8\) (x and y have the same sign). Multiple choices. Not sufficient.

Answer: A.
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The sum of n consecutive positive integers is 45 07 Dec 2014, 15:30
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3. Multiplication of the two digit numbers wx and cx, where w,x and c are unique non-zero digits, the product is a three digit number. What is w+c-x?
(1) The three digits of the product are all the same and different from w c and x.
(2) x and w+c are odd numbers.

(1) wx+cx=aaa (111, 222, ... 999=37*k) --> As x is the units digit in both numbers, a can be 1,4,6 or 9 (2,3,7 out because x^2 can not end with 2,3, or 7. 5 is out because in that case x also should be 5 and we know that x and a are distinct numbers).
1 is also out because 111=37*3 and we need 2 two digit numbers.




////
Could you please explain for me what does unique non zero ?
>>> I feel that question is so silly but I had studied math in different language ( Arabic ) so I really have problem with many terms :cry:

second question is WHY you said aaa=37 k I could not undersand from where it comes
Thank you a lot I learn from here a lot of useful things .
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The sum of n consecutive positive integers is 45 08 Dec 2014, 04:30
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3. Multiplication of the two digit numbers wx and cx, where w,x and c are unique non-zero digits, the product is a three digit number. What is w+c-x?
(1) The three digits of the product are all the same and different from w c and x.
(2) x and w+c are odd numbers.

(1) wx+cx=aaa (111, 222, ... 999=37*k) --> As x is the units digit in both numbers, a can be 1,4,6 or 9 (2,3,7 out because x^2 can not end with 2,3, or 7. 5 is out because in that case x also should be 5 and we know that x and a are distinct numbers).
1 is also out because 111=37*3 and we need 2 two digit numbers.




////
Could you please explain for me what does unique non zero ?
>>> I feel that question is so silly but I had studied math in different language ( Arabic ) so I really have problem with many terms :cry:

second question is WHY you said aaa=37 k I could not undersand from where it comes
Thank you a lot I learn from here a lot of useful things .
Show more

Digits are ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Non-zero digits are all of them except 0: 1, 2, 3, 4, 5, 6, 7, 8, and 9. Unique means that w,x and c are are all different from one another. Thus w, x and c are unique non-zero digits of the two digit numbers wx and cx means that w, x, and c are 1, 2, 3, 4, 5, 6, 7, 8, or 9.

As for 37k, each of the numbers 111, 222, ..., 999 are multiples of 37.

Hope it's clear.
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The sum of n consecutive positive integers is 45 11 Apr 2018, 09:22
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1. The sum of n consecutive positive integers is 45. What is the value of n?
(1) n is even
(2) n < 9

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/the-sum-of-n ... 26861.html


2. Is a product of three integers XYZ a prime?
(1) X=-Y
(2) Z=1

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/is-a-product ... 63139.html


3. Multiplication of the two digit numbers wx and cx, where w,x and c are unique non-zero digits, the product is a three digit number. What is w+c-x?
(1) The three digits of the product are all the same and different from w c and x.
(2) x and w+c are odd numbers.

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/in-multiplic ... 63142.html


4. Is y – x positive?
(1) y > 0
(2) x = 1 – y

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/is-y-x-posit ... 03882.html


5. If a and b are integers, and a not= b, is |a|b > 0?
(1) |a^b| > 0
(2) |a|^b is a non-zero integer

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-a-and-b-a ... 40295.html


6. If M and N are integers, is (10^M + N)/3 an integer?
1. N = 5
2. MN is even

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-m-and-n-a ... 05308.html


7. If b, c, and d are constants and x^2 + bx + c = (x + d)^2 for all values of x, what is the value of c?
(1) d = 3
(2) b = 6

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-b-c-and-d ... 05823.html


8. If x and y are non-zero integers and |x| + |y| = 32, what is xy?
(1) -4x - 12y = 0
(2) |x| - |y| = 16

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-x-and-y-a ... 82076.html


9. Is the integer n odd
(1) n is divisible by 3
(2) 2n is divisible by twice as many positive integers as n

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/is-the-integ ... 91399.html


10. The sum of n consecutive positive integers is 45. What is the value of n?
(1) n is odd
(2) n >= 9

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/the-sum-of-n ... 63143.html
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