December 11, 2018 December 11, 2018 09:00 PM EST 10:00 PM EST Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST. December 13, 2018 December 13, 2018 08:00 AM PST 09:00 AM PST What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51100

If a = b, and c = d, is a = c?
[#permalink]
Show Tags
23 Feb 2016, 01:54
Question Stats:
74% (01:07) correct 26% (01:16) wrong based on 231 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Aug 2009
Posts: 7099

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
23 Feb 2016, 08:59
Bunuel wrote: If a = b, and c = d, is a = c?
(1) b = d (2) b = d
Kudos for correct solution. Hi, Since it is dealing with modulus, lets see what info we get from the Q..
Quote: If a = b, and c = d, is a = c? a=c means that irreespective of sign of b and d, the answer will be YES, if b and d have SAME NUMERIC VALUE.. lets see the choices.. (1) b = d same numeric value.. suff
(2) b = d same numeric value.. suff D
_________________
1) Absolute modulus : http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effectsofarithmeticoperationsonfractions269413.html
GMAT online Tutor



Current Student
Status: Persevere
Joined: 08 Jan 2016
Posts: 119
Location: Hong Kong
GPA: 3.52

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
23 Feb 2016, 09:11
Bunuel wrote: If a = b, and c = d, is a = c?
(1) b = d (2) b = d
Kudos for correct solution. Statement 1: b = d This implies that either b = d or b = d [Though, we will also get b = d and b = d, we can ignore them as they are equivalent to b = d and b = d] First consider, b = d replacing b = a and d = c, we get a = c. Hence, a = c Now, consider, b = d Again, replacing b = a and d = c, we get a = c Hence, a = c Therefore, in either case we are able to answer the question is a = c = 0? with a definitive 'yes'. Hence, statement 1 is sufficient. Options B, C and E are ruled out. Statement 2: b = d Again, replacing b = a and d = c, we get a = c Hence, a = c Therefore, we are able to answer the question is a = c = 0? with a definitive 'yes'. Hence, statement 2 is also sufficient. Option A is also ruled out. The correct answer, therefore, is D



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6619
GPA: 3.82

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
23 Feb 2016, 17:57
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution. If a = b, and c = d, is a = c? (1) b = d (2) b = d When you modify the original condition and the question, they become a=c?> b=d?> b=d or d?, which makes 1)=2). Also, each of them is yes, which is sufficient. Therefore, the answer is D. Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The oneandonly World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only $99 for 3 month Online Course" "Free Resources30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons  try it yourself"



Director
Joined: 24 Nov 2015
Posts: 521
Location: United States (LA)

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
10 May 2016, 13:20
From the question it is clear that we have to check if numerical values of a and c are equal (signs will not matter) Statement 1 says b = d . It clearly shows that a = c as a = b and c = d so sufficient Statement 2 says b = d. It clearly tells that numerical value of b and d is same which in turn says a = c so sufficient Correct answer  D



Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 1268
Location: India
WE: Engineering (Other)

If a = b, and c = d, is a = c?
[#permalink]
Show Tags
19 Nov 2017, 03:46
chetan2u Bunuel VeritasPrepKarishma niks18I am really confused about opening modulus in both sides of equality in spite of going through chetan2u signature I could get away by simply substituting a and c for b and d resp to establish suff for St 1 but St 2 was confusing. Can you please add your two cents?
_________________
It's the journey that brings us happiness not the destination.



PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1217
Location: India
GPA: 3.82

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
19 Nov 2017, 22:49
adkikani wrote: chetan2u Bunuel VeritasPrepKarishma niks18I am really confused about opening modulus in both sides of equality in spite of going through chetan2u signature I could get away by simply substituting a and c for b and d resp to establish suff for St 1 but St 2 was confusing. Can you please add your two cents? Hi adkikanimod is always positive, so if \(x<0\) i.e negative then \(x =x\) for eg. if \(x=3\) then \(3=(3)=3\) so for Statement 2: \(b=d\) is simply \(b=d\), apply mod on both sides which in turn is \(b=d\), now substitute the value of \(b\) & \(d\) to get \(a=c\) Alternatively, we are asked is \(a=c\), square both sides to remove mod. so the question becomes Is \(a^2=c^2\)? Statement 2: \(b=d\), substitute the value of \(b\) & \(d\) to get \(a=c\). Now square both sides to get \(a^2=c^2\). Sufficient



Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 1268
Location: India
WE: Engineering (Other)

If a = b, and c = d, is a = c?
[#permalink]
Show Tags
19 Nov 2017, 23:02
Hi niks18Quote: mod is always positive, so if \(x<0\) i.e negative then \(x =x\)
for eg. if \(x=3\) then \(3=(3)=3\)
how did you use above knowledge to infer below : Quote: \(b=d\), apply mod on both sides
which in turn is \(b=d\), To be more specific, \(b=d\), note that we do not know whether b or d is less than zero but all we know is that b and d have opposite signs. Let me know if I missed anything.
_________________
It's the journey that brings us happiness not the destination.



PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1217
Location: India
GPA: 3.82

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
20 Nov 2017, 00:19
adkikani wrote: Hi niks18Quote: mod is always positive, so if \(x<0\) i.e negative then \(x =x\)
for eg. if \(x=3\) then \(3=(3)=3\)
how did you use above knowledge to infer below : Quote: \(b=d\), apply mod on both sides
which in turn is \(b=d\), To be more specific, \(b=d\), note that we do not know whether b or d is less than zero but all we know is that b and d have opposite signs. Let me know if I missed anything. Hi adkikaniAs I mentioned mod is always positive, because it represents the distance from the 0point in the number line and distance cannot be negative. so irrespective of the value of b or d; d=d let b=2 then b=d will result in d=2 So 2=2 and 2=(2)=2=2 so we have b=d =>b=d



Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 1268
Location: India
WE: Engineering (Other)

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
20 Nov 2017, 05:42
niks18Crystal clear now. +1 Kudos
_________________
It's the journey that brings us happiness not the destination.



VP
Status: It's near  I can see.
Joined: 13 Apr 2013
Posts: 1339
Location: India
Concentration: International Business, Operations
GPA: 3.01
WE: Engineering (Consulting)

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
08 Mar 2018, 23:46
niks18 wrote: adkikani wrote: chetan2u Bunuel VeritasPrepKarishma niks18I am really confused about opening modulus in both sides of equality in spite of going through chetan2u signature I could get away by simply substituting a and c for b and d resp to establish suff for St 1 but St 2 was confusing. Can you please add your two cents? Hi adkikanimod is always positive, so if \(x<0\) i.e negative then \(x =x\) for eg. if \(x=3\) then \(3=(3)=3\) so for Statement 2: \(b=d\) is simply \(b=d\), apply mod on both sides which in turn is \(b=d\), now substitute the value of \(b\) & \(d\) to get \(a=c\) Alternatively, we are asked is \(a=c\), square both sides to remove mod. so the question becomes Is \(a^2=c^2\)? Statement 2: \(b=d\), substitute the value of \(b\) & \(d\) to get \(a=c\). Now square both sides to get \(a^2=c^2\). Sufficient Hey niks18, Red part marked above is inconsistent as to my understanding absolute values are always nonnegative rather than always positive. Please clarify. QZ
_________________
"Do not watch clock; Do what it does. KEEP GOING."



PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1217
Location: India
GPA: 3.82

Re: If a = b, and c = d, is a = c?
[#permalink]
Show Tags
09 Mar 2018, 10:56
QZ wrote: niks18 wrote: adkikani wrote: chetan2u Bunuel VeritasPrepKarishma niks18I am really confused about opening modulus in both sides of equality in spite of going through chetan2u signature I could get away by simply substituting a and c for b and d resp to establish suff for St 1 but St 2 was confusing. Can you please add your two cents? Hi adkikanimod is always positive, so if \(x<0\) i.e negative then \(x =x\) for eg. if \(x=3\) then \(3=(3)=3\) so for Statement 2: \(b=d\) is simply \(b=d\), apply mod on both sides which in turn is \(b=d\), now substitute the value of \(b\) & \(d\) to get \(a=c\) Alternatively, we are asked is \(a=c\), square both sides to remove mod. so the question becomes Is \(a^2=c^2\)? Statement 2: \(b=d\), substitute the value of \(b\) & \(d\) to get \(a=c\). Now square both sides to get \(a^2=c^2\). Sufficient Hey niks18, Red part marked above is inconsistent as to my understanding absolute values are always nonnegative rather than always positive. Please clarify. QZ Hi QZYou are right that mod is "Always Non negative" i.e. either positive or 0. I think either I missed mentioning 0 or I might had wrote that statement in the context of the question. Anyways thanks for highlighting.




Re: If a = b, and c = d, is a = c? &nbs
[#permalink]
09 Mar 2018, 10:56






