BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Featured Course
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
Target question: Is x² − y² divisible by 8?rakeshd347 wrote:Is x² − y² divisible by 8?
(1) x and y are even integers.
(2) x+y is divisible by 8.
To be honest, I first thought the correct answer was B, but then I realized that I had assumed that x and y are integers. If x and y are not necessarily integers, then statement B is not sufficient.abhi.iitb wrote:Hello Brent,
I think the answer for this Q is B, since x+ y is always a factor of x2-y2 so statement B is sufficient to answer this question. Infact, case b in statement 2 is divisible by 8 if we actually perform the calculation.
Please tell me if I am missing anything here.
Abhishek
Divisible by 8 means answer should be integer. Here, answer is not an integer!kuzzden wrote:Case b: x = 7.9 and y = 0.1
Here, x² - y² = 62.4
We may say that 62.4 is divisible by 8, but the answer is not an integer, since there is no requirement that either x or y or both be integers
So ans is B. Or am I missing smth?
This is a tricky question and the trap answer is crafted nicely. If you don't give due care to whether x and y are integer you will definitely get it wrong. I initially though x+y is divisible by 8 done bang. Then thought it can't be so easy let me think and then came across this trap.abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
I agree with you "riz_gmat" .. if we go on dividing into decimals than nearly all numbers are divisible to every other number; we must restrict to Quotient Integerriz_gmat wrote:abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
According to my knowledge, When GMAT asks whether x is divisible y, they mean "when x is divided by y the remainder is zero" . In this case we have decimal point in our ans, and we use decimal point while dividing, when we have a non zero remainder.
Experts, kindly clarify!
If we divide any terminating decimal by 8, the result (quotient) will always be terminating.abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
You'll find that most (if not all) GMAT divisibility questions involve integers.riz_gmat wrote:abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
According to my knowledge, When GMAT asks whether x is divisible y, they mean "when x is divided by y the remainder is zero" . In this case we have decimal point in our ans, and we use decimal point while dividing, when we have a non zero remainder.
Experts, kindly clarify!
I agree with Brent that it not likely to an gmat question. However, it is a good question to gain knowledge and some take away from this. Don't assume numbers integer until unless it is mentioned.Brent@GMATPrepNow wrote:You'll find that most (if not all) GMAT divisibility questions involve integers.riz_gmat wrote:abhi.iitb wrote:I totally agree with Kuzzden,
@riz_gmat: I believe divisibility by 8 means that we get terminating no if we divide 62.4 with 8 which is the case here. Suppose we had 62.5 instead of 62.4 then we would have said that number is not divisible by 8 since the dividend comes out to be non-terminating.
Experts, seek your guidance on this concept.
According to my knowledge, When GMAT asks whether x is divisible y, they mean "when x is divided by y the remainder is zero" . In this case we have decimal point in our ans, and we use decimal point while dividing, when we have a non zero remainder.
Experts, kindly clarify!
In fact, the OG defines divisibility (divisors) as follows:
If x and y are integers and x ≠0, then x is a divisor (factor) of y provided that y = xn for some integer n.
So, you won't be asked whether some non-integer is divisible by an integer.
Given all of this, I'd say that it's unlikely that this could ever be an official GMAT question.
Cheers,
Brent
New here Create free account
