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GMAT 1: 690 Q49 V35
Posts: 124
Updated on: 17 Jun 2017, 02:10
Originally posted by bkpolymers1617 on 17 Jun 2017, 01:45.
Last edited by Bunuel on 17 Jun 2017, 02:10, edited 1 time in total.
Last edited by Bunuel on 17 Jun 2017, 02:10, edited 1 time in total.
Renamed the topic and edited the question.
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Difficulty:
45%
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Question Stats:
68% (01:58) correct
32%
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wrong
based on 276
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If a and b are positive numbers, is a < b?
(1) a < b/2 + 2
(2) a < b/2 -2
(1) a < b/2 + 2
(2) a < b/2 -2
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
If a and b are positive numbers, is a < b?
(1) a < b/2 + 2. If b = 2 and a = 2, then answer is NO but if b = 4 and a = 1, then the answer is YES. Not sufficient.
(2) a < b/2 - 2. Notice that b/2 is less than b, so b/2 - 2 is even less. So, even if b/2 - 2 is greater than a, then so must be b alone. Sufficient.
Answer: B.
_________________
(1) a < b/2 + 2. If b = 2 and a = 2, then answer is NO but if b = 4 and a = 1, then the answer is YES. Not sufficient.
(2) a < b/2 - 2. Notice that b/2 is less than b, so b/2 - 2 is even less. So, even if b/2 - 2 is greater than a, then so must be b alone. Sufficient.
Answer: B.
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S1 -> if b = 2 then a < 3 so it can be 2 but if b = 4, a < 6 so it can be 5 and can be 1. Insufficient
S2 -> b = 2 then a < -1, if b = 4 a < 0. Sufficient.
Answer is B.
Sent from my iPhone using GMAT Club Forum
S2 -> b = 2 then a < -1, if b = 4 a < 0. Sufficient.
Answer is B.
Sent from my iPhone using GMAT Club Forum
Posts: 6,727
bkpolymers1617
Target question: Is a < b?
Given: a and b are positive numbers
Statement 1: a < b/2 + 2
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of a and b that satisfy statement 1. Here are two:
Case a: a = 0 and b = 2, in which case a < b
Case b: a = 2.5 and b = 2, in which case a > b
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, read my article: https://www.gmatprepnow.com/articles/dat ... lug-values
Statement 2: a < b/2 - 2
Since b is POSITIVE, we know that b/2 < b
We can also say that b/2 - 2 < b/2
We can COMBINE these inequalities to get: a < b/2 - 2 < b/2 < b
If we ignore the middle parts, we see that a < b
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer:
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