What is #18+22+26+30+...+50=#?

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Answer 1 · 2017-12-06T08:45:45

#S_n=306#

Assuming that #n_1=18, n_2=22, ...#

#22-18=4#
#26-22=4#

#18+(n-1)4=18+4n-4=4n+14#

#4n+14=50#

#4n=36#

#n=36/4=9#

The last term occurs at #n=9#

#S_n=1/2n(a+l)#

#n# = number of terms
#a# = first term
#l# = last term

#S_n=1/2 *9(18+50)#

#=4.5(68)#

#=306#