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If the two horizontal lines in the figure provided are parallel, what

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If the two horizontal lines in the figure provided are parallel, what [#permalink]

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If the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

Kudos for a correct solution.

[Reveal] Spoiler:
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[Reveal] Spoiler: OA

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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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Answer: (B)
(2) alone is sufficient.

Let's consider these one-by-one:

(1) a+f = 180

This does not provide any information we don't already have. If the lines are parallel, the following equalities hold -
a = d (opposite angles)
a = e (corresponding angles)
b + d = 180
a + b = 180
e + f = 180
d + f = 180
b = f and so on.

So, we already know that a + f = 180.

This is not helpful in finding (a + f + d) – (e + h), as we don't know any of these values.

(2) a - f = 60

This is SUFFICIENT:

a + f = 180 (because a = d and d+f = 180, which is because d + b = 180 and b = f)
a - f = 60

So, 2a = 240

or a = 120

Also, a = d so d = 120; f = 180 - a = 60 ; e = a = 120 ; h = e = 120

So, we can evaluate (a + f + d) – (e + h).

Hence sufficient.


Answer: (B)
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If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 11 Sep 2015, 02:43
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Question Stem is a + f + d - e - h = ?

Since , a = e & h = d ( Corresponding angles )

1) Question Stem can be re- written as following

a + f + d - a - d ( Substituting e & h with a & d )

a + f +d -a -d
SO the question is asking for the value of angle f alone.

2 ) Statement 1. a + f = 180.
As this information can be derived from the diagram itself, it is no additional information. Hence Insufficient.

3) Statement 2. a - f = 60................. Eq 1.
Since we know a + f = 180 ( sum of angles on same straight line ) .........................Eq 2.

Adding Eq 1 & Eq 2 => a = 120.

This is suffucient information to find what the questions seeks. Therefore sufficient.

Ans is B.
:-D :-D :)

Last edited by goldfinchmonster on 11 Sep 2015, 04:03, edited 2 times in total.
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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If the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

answer (B)
(a + f + d) – (e + h)?
a=e & d=h ( corresponding angles)

so a+f+d-a-d=f
To find f, we need two equations but we know that a+f=180
So we only need a-f=60
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 11 Sep 2015, 05:57
If the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

(a + f + d) – (e + h) = a + f + d - d -a = f on applying alternate angle theory --- as e =d and a =h
so f =?

st 1. a+f =180
hence 1 not sufficient


st 2. a -f =60
and f =b ( corresponding angle )

so a-b =60 ----- a
and a+b = 180 ---- b(angle on a straight line equal 180 )

solving a and b we get a = 240/2= 120
and therefore f = 60

B sufficient

Ans
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 11 Sep 2015, 11:49
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The question stem says the horizontal lines are parallel.

Using this information we can deduce,
a = d -------------------(1) (opposite angles)

a= e ------------------(2) (corresponding angles)

e= h ------------------(3) (opposite angles) , therefore a = h

d + f = 180
from (1)
a + f = 180 ----------- (4)

using this info in the equation (a + f + d) – (e + h)

180 + a - 2a => 180 - a --------------- (5)

Statement 1:

a + f = 180 => same as eq. (4) . No new info. Cannot get the value - Insufficient

statement 2

a – f = 60 ------------- (6)
from (4) and (6) can find the value of a
substitute in (5) we can find the value of (a + f + d) – (e + h)

Ans B => Statement 2 sufficient
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 12 Sep 2015, 04:28
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answer is B.

f=c (parallel lines having same interception)
hence, a+c or a+f=180
B gives that a-f=60

solving for both we get the vales for a and f.
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 12 Sep 2015, 09:13
Bunuel wrote:
Image
If the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

Kudos for a correct solution.

[Reveal] Spoiler:
Attachment:
Picture-3.png


Given : From Parallel Line case,
a = d = e = h
b = c = f = g


Question : what is (a + f + d) – (e + h) = (a+f+a) - (a+a) = f = ?

Statement 1: a + f = 180
a is Unknown Hence f can't be calculated
Also, a+f=180 is a Universal Truth (Supplementary angles) and no extra information so this can't be used to answer the question because we are expected to know about this information
NOT SUFFICIENT

Statement 2: a - f = 60
Also, We know a+f=180 (Supplementary angles)
i.e. a = 120 and f = 60
SUFFICIENT

Answer: option B
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Expert Post
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 14 Sep 2015, 06:55
Bunuel wrote:
Image
If the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

Kudos for a correct solution.

[Reveal] Spoiler:
Attachment:
Picture-3.png


GROCKIT OFFICIAL SOLUTION:

This question solely relies on our knowledge of angle measures and parallel lines. Angles a and b are complementary (add up to 180, a straight line), and angles b and f are congruent, so we already know that a + f = 180 without Statement (1) telling us. (a + f + d) – (e + h) = a + f + d – e – h = 180 – h. Since we do not know the exact value of h (the difference between the obtuse and acute angles), Statement (1) is not sufficient. Statement (2) gives us the difference between the obtuse and acute angle, and so it is sufficient.
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Resources:
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 15 Sep 2015, 08:32
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 the two horizontal lines in the figure provided are parallel, what is (a + f + d) – (e + h)?

(1) a + f = 180

(2) a – f = 60

Transforming the original condition and the question, we have a=d=e=h thus (a + f + d) – (e + h)?--> f=?. a+f=180 we have 2 variables (a,f), and 1 equation (a+f=180) therefore we need 1 more equation. Therefore there is high probability that D is the answer

In case of 1), a+f=180 is the repetition of the original condition. Therefore the condition is not sufficient.
In case of 2), a-f=60 and a+f=180 gives us 2f=120, f=60. Therefore the condition is sufficient, and the answer is B.
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 23 Oct 2015, 09:33
This is what you call a trick question.... How I fell for it... C trap question ...
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Re: If the two horizontal lines in the figure provided are parallel, what [#permalink]

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New post 11 Apr 2017, 03:50
nikhiljd wrote:
This is what you call a trick question.... How I fell for it... C trap question ...


A + B = 180
B = F
A + F = 180
Therefore you should skip this option first of all :)
Re: If the two horizontal lines in the figure provided are parallel, what   [#permalink] 11 Apr 2017, 03:50
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