Find the sum of arithmetic sequence Sum of integers between 6 and 30 ??

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Answer 1 · 2018-06-25T20:24:26

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Here you are solving #sum_(r=6) ^30 r #

# sum_(r=6) ^30 r = sum_(r=1) ^30 r - sum_(r=1) ^5 r #

Use:

#sum_(r=1) ^n r = n/2 (n+1) #

# = 30/2(30+1) - 5/2(5+1) #

# = 450 #

from 6 to 30, inclusive is 450

from 6 to 30, exclusive is #450 - 6 - 30 = 414 #