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17 Oct 2018, 00:38
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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:
57% (01:49) correct
43%
(01:56)
wrong
based on 180
sessions
History
Date
Time
Result
Not Attempted Yet
What is the length of the line AD?
(1) AC = 10, BD = 15
(2) AB/BC = BC/CD
Attachment:
2018-10-17_1136.png [ 2.1 KiB | Viewed 4427 times ]
Pure algebraic questions like this one are no longer part of the GMAT Data Sufficiency syllabus.
For relevant Data Sufficiency questions, please check the Data Sufficiency forum:
Data Sufficiency Forum
Data Sufficiency Forum
17 Oct 2018, 19:16
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From statement 1:
AC = AB+BC = 10
BD = BC+CD = 15
AD = AB+BC+CD. Since BC is unknown. We cant determine the length of AD.
Insufficient.
From statement 2:
\(\frac{AB}{BC}\) = \(\frac{BC}{CD}\) Cross multiplying gives \(BC^2\) = AB*CD.
Clearly Insufficient.
Combining both From 1:
AB = 10-BC
CD = 15-BC
From 2 \(BC^2\) = AB*CD = (10-BC)(15-BC)
Solving gives BC as 6.
Hence AD becomes 19.
Sufficient.
C is the aswer.
AC = AB+BC = 10
BD = BC+CD = 15
AD = AB+BC+CD. Since BC is unknown. We cant determine the length of AD.
Insufficient.
From statement 2:
\(\frac{AB}{BC}\) = \(\frac{BC}{CD}\) Cross multiplying gives \(BC^2\) = AB*CD.
Clearly Insufficient.
Combining both From 1:
AB = 10-BC
CD = 15-BC
From 2 \(BC^2\) = AB*CD = (10-BC)(15-BC)
Solving gives BC as 6.
Hence AD becomes 19.
Sufficient.
C is the aswer.
21 Mar 2021, 16:54
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Chethan92
How come statement 1 is insufficient? I get that we don't know BC, but why would that matter?
Suppose BC = 3, then AB = 7 and CD = 12
No matter what value we choose for BC, so long as we adjust for the overlap, the length will always be 22?
What am I missing?
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