5.2.3 Sum of the First nTerms of an Arithmetic Progression
(F) Sum of the First n terms of an Arithmetic Progressions
a = first term
d = common difference
n = the number of term
Sn = the sum of first n terms
Calculate the sum of each of the following arithmetic progressions.
(a) -11, -8, -5, … up to the first 15 terms.
(b) 8, 10½, 13,… up to the first 13 terms.
(c) 5, 7, 9,….., 75 [Smart TIPS: The last term is given, you can find the number of term, n]