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# For positive integer values of n, the operation n# is defined as the

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Math Expert
Joined: 02 Sep 2009
Posts: 56257
For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 01:17
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Difficulty:

35% (medium)

Question Stats:

65% (01:05) correct 35% (01:18) wrong based on 192 sessions

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For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

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Joined: 28 Jan 2013
Posts: 31
Location: United States
GPA: 3.1
WE: Information Technology (Consulting)
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 02:09
3
15# – 14# = k#
15 + 14# - 14# = k#
15 = k#

Ans:E
Intern
Joined: 02 Jul 2014
Posts: 4
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 05:47
1
Bunuel wrote:
For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

If you are asking K# then it is : 15#-14#= 15 ---> E
Else if you are asking K, then it is K=5---->C
CEO
Joined: 20 Mar 2014
Posts: 2620
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 06:31
dhawalbp wrote:
Bunuel wrote:
For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

If you are asking K# then it is : 15#-14#= 15 ---> E
Else if you are asking K, then it is K=5---->C

Director
Joined: 21 May 2013
Posts: 655
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 08:35
1
Bunuel wrote:
For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

15#=1+2+3+4.....+15=120
14#=1+2+#+4....+14=105

15#-14#=15
Now, 15=k#
Manager
Joined: 20 Jul 2011
Posts: 79
GMAT 1: 660 Q49 V31
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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17 Jul 2015, 13:13
2
Bunuel wrote:
For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

Sum of first n numbers is = n(n+1)/2
here,
K# = 15# - 14#
K# = (15*16)/2 - (14*15)/2

Solving K# = 15(8-7) = 15. Option E.
Math Expert
Joined: 02 Sep 2009
Posts: 56257
Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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19 Jul 2015, 13:00
Bunuel wrote:
For positive integer values of n, the operation n# is defined as the sum of all integers from 1 to n, inclusive. For example, 4# = 1 + 2 + 3 + 4 = 10. If 15# – 14# = k#, what is the value of k#?

A. 1
B. 4
C. 5
D. 14
E. 15

Kudos for a correct solution.

800score Official Solution:

The symbol # is a function. These types of functions are common on the GMAT. Using the definition of n#, we know that:
15# – 14# = (1 + 2 +…+ 15) – (1 + 2 +…+ 14) = 15.

So k# must equal 15, or choice (E).
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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21 Dec 2018, 17:58
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Re: For positive integer values of n, the operation n# is defined as the   [#permalink] 21 Dec 2018, 17:58
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