How do you find the sum of #Sigma 5# where k is [1,5]? Calculus Introduction to Integration Sigma Notation 1 Answer Alan N. Mar 17, 2017 #sum_"k=1,5" k = 15# Explanation: The sum of the first #k# natural numbers is given by: #(k(k+1))/2# Hence: #sum_"k=1,5" k = (5(5+1))/2 = (5*6)/2 = 15# Answer link Related questions How does sigma notation work? How do you use sigma notation to represent the series #1/2+1/4+1/8+…#? Use summation notation to express the sum? What is sigma notation for an arithmetic series with first term #a# and common difference #d# ? How do you evaluate the sum represented by #sum_(n=1)^5n/(2n+1)# ? How do you evaluate the sum represented by #sum_(n=1)^(8)1/(n+1)# ? How do you evaluate the sum represented by #sum_(n=1)^(10)n^2# ? What is sigma notation for a geometric series with first term #a# and common ratio #r# ? What is the value of #1/n sum_{k=1}^n e^{k/n}# ? Question #07873 See all questions in Sigma Notation Impact of this question 2303 views around the world You can reuse this answer Creative Commons License