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If there are 13 boys in club X, what is the average age of these boys?
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23 May 2020, 08:00
23 May 2020, 08:00
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Difficulty:
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Question Stats:
90% (00:53) correct
10%
(00:47)
wrong
based on 194
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If there are 13 boys in club X, what is the average age of these boys?
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
(2) Eleven of the boys are either 10 years old or 11 years old.
ID: 700134
DS21210
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
(2) Eleven of the boys are either 10 years old or 11 years old.
ID: 700134
DS21210
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6797
Given Kudos: 799
Location: Canada
Re: If there are 13 boys in club X, what is the average age of these boys?
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23 May 2020, 08:24
23 May 2020, 08:24
Expert Reply
Top Contributor
Bunuel
If there are 13 boys in club X, what is the average age of these boys?
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
(2) Eleven of the boys are either 10 years old or 11 years old.
DS21210
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
(2) Eleven of the boys are either 10 years old or 11 years old.
DS21210
Target question: What is the average age of the 13 boys?
When I SCAN the two statements, they both feel insufficient, AND I’m pretty sure I can identify some cases with conflicting answers to the target question. So, I’m going to head straight to……
Statements 1 and 2 combined
There are several scenarios that satisfy BOTH statements. Here are two:
Case a: The ages are {9, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 13}.
Case b: The ages are {9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 13}
Since the two sets have DIFFERENT sums, we know that the averages will be DIFFERENT
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
Re: If there are 13 boys in club X, what is the average age of these boys?
[#permalink]
03 Sep 2021, 22:20
03 Sep 2021, 22:20
given: a1, a2, ..., a13
Ask: avrg = ?
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
=> Max = 13, min = 9
=> definitely insufficient
(2) Eleven of the boys are either 10 years old or 11 years old.
a2, a3,...,a12 = 10 or 11
=> definitely insufficient
(1) & (2): we still dont know the other 11 numbers are 10 or 11
=> insufficient
=> E
Posted from my mobile device
Ask: avrg = ?
(1) The oldest boy is 13 years old and the youngest boy is 9 years old.
=> Max = 13, min = 9
=> definitely insufficient
(2) Eleven of the boys are either 10 years old or 11 years old.
a2, a3,...,a12 = 10 or 11
=> definitely insufficient
(1) & (2): we still dont know the other 11 numbers are 10 or 11
=> insufficient
=> E
Posted from my mobile device
