Hello,
I could use some help. I've been working on number properties today in the guidebook I purchased specifically for NPs. I admit that NPs are a very large weakness for me, so the errors are probably on met, but I've gone over the following three problems several times using DS strategies and my answers don't match the guidebook. I went to the errata website and no errors were listed for the odd/even CHPT. Finding three unlisted errors in one CHPT has got to be me, but I'd like to see what the rest of the forum comes up with their own answers to see if it matches mine or the book. Thanks for your help.
1. If x>1, what is the value of x?
1) There are x unique factors of x.
2) The sum of x and any prime number larger than x is odd.
2. What is the remainder when a is divided by 4?
1) a is the square of an odd integer.
2) a is a multiple of 3.
3. This is not a DS question, instead you were to answer if x is odd, even, or can't be determined & ALL VARIABLES ARE INTEGERS -
- If x/y yields an odd integer, what is x?
Possible errors in Number Property Guide for odd/even(s)
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- murphydb711
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Minimum possible value of x is 2.murphydb711 wrote:1. If x > 1, what is the value of x?
1) There are x unique factors of x.
2) The sum of x and any prime number larger than x is odd.
Statement 1: For x to have x unique factors, x must be divisible by all the integers starting from 1 to x. But for any x greater than 2, x and (x - 1) will be coprime integers. Hence, for any x > 2, it is not possible that (x - 1) will be a factor of x. Only possible value of x is 2.
Sufficient
Statement 2: (x + p) is odd, where p is a prime number such that p > 2
All prime numbers greater than p are odd. Hence, x must be even.
Now x can have any even value. For example,
- x = 2, p = 5
x = 4, p = 5
The correct answer is A.
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Q1. x > 1 (given)
what is x?
ST1: there are x unique factors of x
lets try a few values for x
if x = 2 (as x>1), factors = 1,2 (satisfies)
if x=3, factors= 1,3 (DOES NOT SATISFY as there are only 2 unique factors of X and X = 2)
x = 4, factors= 1,2,4 (DOES NOT SATISFY as there are 3 unique factors of X and x = 4)
There is no numbers besides 2 that will satisfy this.
hence St1 is sufficient.
St2: sum of x and any prime larger than x = odd
Odd = odd + Even or Odd = Even + odd
if x = 2, prime no = 3 sum = odd
but if x = 3, prime no = 5 (odd) then sum = even (odd + odd = even)
not sufficient
Hence IMO it should be A
what is x?
ST1: there are x unique factors of x
lets try a few values for x
if x = 2 (as x>1), factors = 1,2 (satisfies)
if x=3, factors= 1,3 (DOES NOT SATISFY as there are only 2 unique factors of X and X = 2)
x = 4, factors= 1,2,4 (DOES NOT SATISFY as there are 3 unique factors of X and x = 4)
There is no numbers besides 2 that will satisfy this.
hence St1 is sufficient.
St2: sum of x and any prime larger than x = odd
Odd = odd + Even or Odd = Even + odd
if x = 2, prime no = 3 sum = odd
but if x = 3, prime no = 5 (odd) then sum = even (odd + odd = even)
not sufficient
Hence IMO it should be A
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Q2. remainder when a / 4 ?
ST1: a = sq of an odd integer
if a = 1, a^2 = 1 and 1/4 = rem 1
if a = 3, a^2 = 9 and 9/4 = rem 1
if a = 5, a^2 = 25 and 25/4 = rem 1
Sufficient
ST2: a = multiple of 3
if a = 3, 3/4 = rem 3
if a = 6, 6/4 = rem 2
Not Sufficient
Hence Ans A
ST1: a = sq of an odd integer
if a = 1, a^2 = 1 and 1/4 = rem 1
if a = 3, a^2 = 9 and 9/4 = rem 1
if a = 5, a^2 = 25 and 25/4 = rem 1
Sufficient
ST2: a = multiple of 3
if a = 3, 3/4 = rem 3
if a = 6, 6/4 = rem 2
Not Sufficient
Hence Ans A
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Statement 1: Let us assume a = (2n + 1)², where n is some non-negative integer.murphydb711 wrote:2. What is the remainder when a is divided by 4?
1) a is the square of an odd integer.
2) a is a multiple of 3.
So, a = (4n² + 4n + 1) = 4*(n² + n) + 1 = (some multiple of 4) + 1
Hence, when a is divided by 4, the remainder is 1.
Sufficient
Statement 2: Consider the following two examples,
a = 0 ---> remainder is 0
a = 3 ---> remainder is 3
Not sufficient
The correct answer is A.
Anju Agarwal
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Q3. if x/y = odd integer, it could either be 9/3 = 3 (where x = odd) or 6/2 = 3 (where x = even)
only with the above information, with no information about y, we cannot for certain say anything about x
only with the above information, with no information about y, we cannot for certain say anything about x
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Consider the following examples,murphydb711 wrote:3. This is not a DS question, instead you were to answer if x is odd, even, or can't be determined & ALL VARIABLES ARE INTEGERS -
- If x/y yields an odd integer, what is x?
x = 1, y = 1 ---> x odd
x = 2, y = 2 ---> x even
Hence, can't be determined.
Anju Agarwal
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Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.
§ GMAT with Gurome § Admissions with Gurome § Career Advising with Gurome §
Quant Expert, Gurome
Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.
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