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
(E) 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).  Although 15# – 14# = 15 what the problem asks is: 15# – 14# = k# So, k# = 15 but k = 5 because k# =1 + 2 + 3 + 4 + 5 = 15 So, the right answer should be C. Please clarify.
