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This problem consists of two series for
1st Series starting with 23,28.33......10 terms
2nd Series starting with 27,32....9 terms

For 1st series,
total number of terms will be 10
and 1stterm =23 & c.d=5
S1=455

Second series will be of 9 terms,
1st term =27 & c.d=5
S2=423

Sum of series = 423+455=878
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ashudhall
23,27,28,32,33,37..we can see that each pair sums up to be 50, 60, 70 and so on till 130 as there 9 pairs
Hence sums up to be 810 till 18th term
Since we know each pair has a difference of 4 therefore 17th and 18th term = 2x+4 =130
17 th term = 63
Hence 19th term = 63+5 =68
Hence sum = 810+68=878

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Hey! This is a really easy solution. My only question is that why is it 2x+4=130 and not 2x+5=130 since the stem mentions that the diff between the alternate numbers is 5?
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