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24 Mar 2020, 06:20
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
63% (02:29) correct
37%
(02:21)
wrong
based on 138
sessions
History
Date
Time
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Not Attempted Yet
In the figure above, if lines r and s are parallel, what is the value of a + b?
(1) c − a = 25
(2) a − d = 15
Attachment:
2020-03-24_1718.png [ 10.31 KiB | Viewed 6039 times ]
ShankSouljaBoi
Joined: 21 Jun 2017
Last visit: 28 Mar 2026
Posts: 595
Own Kudos:
Given Kudos: 4,090
Location: India
Concentration: Finance, Economics
Schools: Rotman '23 (D) IIMA PGPX'22 (D) Desautels '23 (D) Schulich Sept '23 (D) WBS (D) IIML IPMX'25 (A)
GMAT 1: 660 Q49 V31
GMAT 2: 620 Q47 V30
GMAT 3: 650 Q48 V31
GPA: 3.1
WE:Corporate Finance (Non-Profit and Government)
Products:
Schools: Rotman '23 (D) IIMA PGPX'22 (D) Desautels '23 (D) Schulich Sept '23 (D) WBS (D) IIML IPMX'25 (A)
GMAT 3: 650 Q48 V31
Posts: 595
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611
27 Mar 2020, 07:38
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27 Mar 2020, 08:51
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Solution:
Step 1:
- • In the given figure, it’s given that line r and s are parallel to each other (shown in diagram below).
• From the diagram, we can infer the following:
- o Notice the vertically possible angle, i.e. angle “a”
o Also, a = b (corresponding angles)
o And c + d = 180 (straight line angle)..........(i)
- Note, using the parallel line information, we are just able to infer that a = b. The remaining two information are general angle/straight line properties.
We need to find the value of a + b or in other words, we need to find the value of either a or b, since both are equal.
Step 2:
Statement 1: c – a = 25
- • We already know that c + d = 180 or c = 180 – d.........(i)
• Also, c – a = 25 or c = 25 + a
- o Equating c, we get
- 25 + a = 180 – d or a + d = 155
- o Hence, statement 1 is not sufficient.
- • Using this information also, we cannot find the value of a.
• Hence, statement 2 is also not sufficient.
Step 3:
- • On combining both statements, we have:
- o a + d = 155 and
o a – d = 15
Hence, the correct answer is Option C.
Probable mistakes, that a student can make:
They may end up assuming the other two lines are parallel too.
- • That will lead them to believe that a = d and a + c = 180
- o This in turn will lead them to think that the answer will be Option A or D, which is incorrect.
