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Find the sum of all the four digit numbers which are formed
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Updated on: 06 Nov 2012, 03:22
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75% (01:43) correct 25% (01:47) wrong based on 333 sessions
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Find the sum of all the four digit numbers which are formed by digits 1, 2, 5, 6 A. 933510 B. 93324 C. 65120 D. 8400
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Originally posted by xcusemeplz2009 on 23 Dec 2009, 06:38.
Last edited by Bunuel on 06 Nov 2012, 03:22, edited 1 time in total.
Renamed the topic and edited the question.




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Re: permutation
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23 Dec 2009, 07:16
xcusemeplz2009 wrote: find the sum of all the four digit numbers which are formed by digits 1,2,5,6
a)933510 b)93324 c)65120 d)8400 The answer choices make the solution easy: There are 4!=24 four digit numbers which are formed by digits 1, 2, 5, 6. Obviously 24/4=6 numbers will end with 1; 6 numbers will end with 2, 6 numbers with 5 and 6 numbers with 6. 6*1+6*2+6*5+6*6=6*14=84, which means that the sum of all these 24 numbers must end by 4, only answer choice with 4 at the end is B. Answer: B. But if we were not given such an easy answer choices, the solution would be: We have 24 numbers of the of the form: 1000a+100b+10c+d, where a, b, c and d can take any value from the set {1, 2, 5, 6} and there will be 6 numbers with same digit (a, b, c, d) at the thousands, hundreds, tens and units digits. (1000*6a+1000*6b+1000*6c+1000*6d)+(100*6a+100*6b+100*6c+100*6d)+(10*6a+10*6b+10*6c+10*6d)+(6a+6b+6c+6d)=(6a+6b+6c+6d)(1111)= =6(a+b+c+d)(1111)=6*14*1111=93324 Generally the sum of all the numbers which can be formed by using the n distinct digits, is given by the formula: (n1)!*(sum of the digits)*(111…..n times)
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Re: Find the sum of all the four digit numbers which are formed
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30 Dec 2013, 08:27
xcusemeplz2009 wrote: Find the sum of all the four digit numbers which are formed by digits 1, 2, 5, 6
A. 933510 B. 93324 C. 65120 D. 8400 3!*1111*(14) will have units digit 4 B is the answer Hope it helps Cheers! J



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Re: Find the sum of all the four digit numbers which are formed
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03 Oct 2017, 23:08
Doesn't 'sum of all' suggest that repetition is allowed ?
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Re: Find the sum of all the four digit numbers which are formed
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11 Oct 2017, 19:45
zvazviri wrote: Doesn't 'sum of all' suggest that repetition is allowed ? I have the same query. Experts, please clarify.



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Re: Find the sum of all the four digit numbers which are formed
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11 Oct 2017, 21:00
gumnamibaba wrote: zvazviri wrote: Doesn't 'sum of all' suggest that repetition is allowed ? I have the same query. Experts, please clarify. No it does not. Ideally it should have been clarified more precisely but it's assumed that we are adding the numbers which could be constructed by rearranging the numbers 1, 2, 5, and 6.
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Re: Find the sum of all the four digit numbers which are formed
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11 Oct 2017, 23:23
Bunuel wrote: gumnamibaba wrote: zvazviri wrote: Doesn't 'sum of all' suggest that repetition is allowed ? I have the same query. Experts, please clarify. No it does not. Ideally it should have been clarified more precisely but it's assumed that we are adding the numbers which could be constructed by rearranging the numbers 1, 2, 5, and 6. Given this ambiguity, it's safe to say this is not an OG problem, and I would not see problems worded similarly on the test?
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Re: Find the sum of all the four digit numbers which are formed
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11 Oct 2017, 23:26
zvazviri wrote: Given this ambiguity, it's safe to say this is not an OG problem, and I would not see problems worded similarly on the test? Yes, this is not a proper GMAT problem not only because of the wording. Notice that it has 4 options not 5.
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Find the sum of all the four digit numbers which are formed
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24 Nov 2018, 04:37
Could also be solved with estimation: \(4*1000 + 4*2000 + 4*5000 + 6*6000=68000\) Just looking at the answer choices option B is the only possible solution.
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Re: Find the sum of all the four digit numbers which are formed
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24 Nov 2018, 10:56
xcusemeplz2009 wrote: Find the sum of all the four digit numbers which are formed by digits 1, 2, 5, 6
A. 933510 B. 93324 C. 65120 D. 8400 1256+6521=7777 7777/2=3888.5 3888.5*4!=93324 B



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Re: Find the sum of all the four digit numbers which are formed
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19 Sep 2019, 09:32
I have made similar mistakes in other problems. Until repetition is not specified in problem, it is safe to proceed considering nonrepetition of digits/letters. And this rule is valid throughout the GMAT. Bunuel wrote: gumnamibaba wrote: zvazviri wrote: Doesn't 'sum of all' suggest that repetition is allowed ? I have the same query. Experts, please clarify. No it does not. Ideally it should have been clarified more precisely but it's assumed that we are adding the numbers which could be constructed by rearranging the numbers 1, 2, 5, and 6.




Re: Find the sum of all the four digit numbers which are formed
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19 Sep 2019, 09:32






