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Which is greater a+d or b+c
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25 Dec 2018, 10:44
25 Dec 2018, 10:44
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\(\frac{a}{b}= \frac{3}{7} = \frac{c}{d}\)
Quantity A |
Quantity B |
\(a+d\) |
\(b+c\) |
A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Which is greater a+d or b+c
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31 Mar 2020, 10:02
31 Mar 2020, 10:02
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Carcass wrote:
\(\frac{a}{b}= \frac{3}{7} = \frac{c}{d}\)
Quantity A |
Quantity B |
\(a+d\) |
\(b+c\) |
A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
Key concept: Just because a/b = 3/7, does not mean a = 3 and b = 7
For example, if a = 12 and b = 28, then a/b = 12/28 = 3/7
Likewise, if a = -30 and b = -70, then a/b = -30/-70 = 3/7
Given the wide variety of possible values, it feels like the correct answer is D
So, let's test some possible values
case i: If \(\frac{a}{b}= \frac{3}{7} = \frac{c}{d}\), then it could be the case that a = 3, b = 7, c = 12 and d = 28:
We get:
Quantity A: \(a+d=3+28=31\)
Quantity B: \(b+c=7+12=19\)
In this case, Quantity A is greater
case ii: If \(\frac{a}{b}= \frac{3}{7} = \frac{c}{d}\), then it could be the case that a = 3, b = 7, c = -30 and d = -70:
We get:
Quantity A: \(a+d=3+(-70)=-67\)
Quantity B: \(b+c=7+(-30)=-23\)
In this case, Quantity B is greater
Answer: D
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General Discussion
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1141
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Re: Which is greater a+d or b+c
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18 Jun 2021, 10:31
18 Jun 2021, 10:31
2
\(\frac{a}{b}= \frac{3}{7}\) then we can take
a = 3x and b = 7x [where x was the common integer which got cancelled when we divided a by b]
\(\frac{3}{7} = \frac{c}{d}\) then we can take
c = 3y and d = 7y [where y was the common integer which got cancelled when we divided c by d]
Quantity A = a + d = 3x + 7y
Quantity B = b + c = 7x + 3y
Now there is no way we can tell whether 3x + 7y = 7x + 3y or not, as we do not know the values of x and y
So, Answer will be D
Hope it helps!
a = 3x and b = 7x [where x was the common integer which got cancelled when we divided a by b]
\(\frac{3}{7} = \frac{c}{d}\) then we can take
c = 3y and d = 7y [where y was the common integer which got cancelled when we divided c by d]
Quantity A = a + d = 3x + 7y
Quantity B = b + c = 7x + 3y
Now there is no way we can tell whether 3x + 7y = 7x + 3y or not, as we do not know the values of x and y
So, Answer will be D
Hope it helps!
