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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
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Bunuel wrote:

GMAT CLUB TESTS' FRESH QUESTION:



{a, b, 1, 2}
If a and b are positive integers less than 10, what is the mode of the list above?

(1) The number of different permutations of the numbers in the list is 12.
(2) A four-digit number 21ab is divisible by 9


Par of GMAT CLUB'S New Year's Quantitative Challenge Set

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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
Bunuel wrote:

GMAT CLUB TESTS' FRESH QUESTION:



{a, b, 1, 2}
If a and b are positive integers less than 10, what is the mode of the list above?

(1) The number of different permutations of the numbers in the list is 12.
(2) A four-digit number 21ab is divisible by 9



# 1:
4!= 24 but given permutation is 12 so 4!/2!= 12 but 2 numbers can be any between (0-10) in sufficient

#2: 21ab is divisible by 9 , so number sum 2+1+a+b= 9 , for which we have many values so in sufficeint

from 1&2 : we wont get any 1 single value to determine the mode... IMO E
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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
chetan2u wrote:
Bunuel wrote:

GMAT CLUB TESTS' FRESH QUESTION:



{a, b, 1, 2}
If a and b are positive integers less than 10, what is the mode of the list above?

(1) The number of different permutations of the numbers in the list is 12.
(2) A four-digit number 21ab is divisible by 9



Mode means the integer repeated max time


(1) The number of different permutations of the numbers in the list is 12.
All four cannot be different, otherwise permutations would be 4!=4*3*2=24
Since there are 12 permutations, and 12=24/2=4!/2=4!/2!
So there is one pair same and other two distinct..
But mode could be any 1, or 2 or a variable
Insufficient

(2) A four-digit number 21ab is divisible by 9
Since divisibility depends on sum of the number, so a+b+2+1=3+a+b is div by 9
Since a be B are interchangeable, we cannot find the value of variable
Number could 2115,2151,2124,2142,2133,2169,2196,2178,2187
So insufficient

Combined
One pair and other two distinct, so possibilities 2115,2124,2133
So mode can be 1,2 or 3
Insufficient

E


Please correct me if I'm wrong

Number of permutations of 4 different terms is 4! which is 24
If 2 are different and 2 similar then number of permutations is 4!/2! which is 12

Statement A says - number of permutations is 12 => 2 elements are similar and 2 are unique => Mode 2 => A is sufficient
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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
SRK780 wrote:
chetan2u wrote:
Bunuel wrote:

GMAT CLUB TESTS' FRESH QUESTION:



{a, b, 1, 2}
If a and b are positive integers less than 10, what is the mode of the list above?

(1) The number of different permutations of the numbers in the list is 12.
(2) A four-digit number 21ab is divisible by 9



Mode means the integer repeated max time


(1) The number of different permutations of the numbers in the list is 12.
All four cannot be different, otherwise permutations would be 4!=4*3*2=24
Since there are 12 permutations, and 12=24/2=4!/2=4!/2!
So there is one pair same and other two distinct..
But mode could be any 1, or 2 or a variable
Insufficient

(2) A four-digit number 21ab is divisible by 9
Since divisibility depends on sum of the number, so a+b+2+1=3+a+b is div by 9
Since a be B are interchangeable, we cannot find the value of variable
Number could 2115,2151,2124,2142,2133,2169,2196,2178,2187
So insufficient

Combined
One pair and other two distinct, so possibilities 2115,2124,2133
So mode can be 1,2 or 3
Insufficient

E


Please correct me if I'm wrong

Number of permutations of 4 different terms is 4! which is 24
If 2 are different and 2 similar then number of permutations is 4!/2! which is 12

Statement A says - number of permutations is 12 => 2 elements are similar and 2 are unique => Mode 2 => A is sufficient



Finding the Mode means finding the value that is most repeated. Not, how many times the value is repeated.

For e.g. in a sample set of ( 1, 1, 1, 2, 3, 3), the mode is 1. not 3. Hope it helps.
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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
so if the set contains (1, 1 and 2,2 and 3,3 ) whats the mode ?
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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
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Re: If a and b are positive integers less than 10, what is the mode of the [#permalink]
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