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

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

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New post 17 Jul 2015, 00:17
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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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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 17 Jul 2015, 01:09
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15# – 14# = k#
15 + 14# - 14# = k#
15 = k#

Ans:E
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 17 Jul 2015, 04:47
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
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 17 Jul 2015, 05:31
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


The question is asking about k# and not k
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 17 Jul 2015, 07:35
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#
Answer E
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 17 Jul 2015, 12:13
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.


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.
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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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New post 19 Jul 2015, 12:00
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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Resources:
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: For positive integer values of n, the operation n# is defined as the  [#permalink]

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