Hi
Can any one help me understand what I am doing wrong. My exam is approaching real fast so would really apprecaite ur help. The link to the actual question is copied below
https://www.beatthegmat.com/ps-t6322.html
Here is what I did
The 5th term in the series is 1 (i.e 5-4)
the 6th term is 2 (i.e 6-4)
The 97th terms is 93
So essentially from the 5th term in the series to the 97th term we have a series of consequitive integers from 1 to 93
So the sum of all consequitive integers from 1 to 93 inclusive =
(94/2) * (94-1+1) = 4418
Now the sum of the first 4 numbers in the sequence is (2 + (-3) + 5 + (-1) ) = 3
So sum of first 97 terms is 4418 + 3 = 4421
This is obviously wrong, but I dont know why. Please Help.
Thanks in advance
Series Question - Please help
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this is repetitive series in which the a(n) = a(n-4)
i.e 5th term = first term & so on
now sum of 4 terms = 2-3+5-1 =3
we need to find the sum of first 97 terms
now we know the series repeats every 5th term
so we can say that the series has chunks of 4 with each having sum =3
(sum of 4 terms like the first 4)
so 97 will have 96 +1 terms 96/4 =24 & the 97th term will be same as first =2 (repetition)
so sum is 24*3 +2 =74
hope this clear.
i.e 5th term = first term & so on
now sum of 4 terms = 2-3+5-1 =3
we need to find the sum of first 97 terms
now we know the series repeats every 5th term
so we can say that the series has chunks of 4 with each having sum =3
(sum of 4 terms like the first 4)
so 97 will have 96 +1 terms 96/4 =24 & the 97th term will be same as first =2 (repetition)
so sum is 24*3 +2 =74
hope this clear.
Regards
Samir
Samir