How do you find the sum of the first 20 terms of the series #3+8+13+18+23+...#?

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Answer 1 · 2016-09-01T23:04:33

The first twenty terms have a sum of #1010#.

In this problem, #a = 3#, #r = 8 - 3 = 5#, #n = 20# and #s_20 = ?#.

We will use the formula #s_n = n/2(2a + (n - 1)d)#

#s_20 = 20/2(2(3) + (20 - 1)5)#

#s_20 = 10(6 + 95)#

#s_20 = 10(101)#

#s_20 = 1010#

Hopefully this helps!