2013Progression (Sequence and Series)Hard
Question
Let 
Then Sn can take value(s)
Then Sn can take value(s)Options
A.1056
B.1088
C.1120
D.1332
Solution
Sn = -12 - 22 + 32 + 42 - 52 - 62 + 72 + 82 .........
Sn = (32 - 12) + (42 - 22) + ............
Sn = 2(1 + 2 + 3 +........ + 4n)
Sn = 4n(4n + 1)
Sn = 4n(4n + 1) = 1056 is possible when n = 8
4n (4n + 1) = 1088 not possible
4n(4n + 1) = 1120 not possible
4n(4n + 1) = 1332 possible when n = 9.
Sn = (32 - 12) + (42 - 22) + ............
Sn = 2(1 + 2 + 3 +........ + 4n)
Sn = 4n(4n + 1)
Sn = 4n(4n + 1) = 1056 is possible when n = 8
4n (4n + 1) = 1088 not possible
4n(4n + 1) = 1120 not possible
4n(4n + 1) = 1332 possible when n = 9.
Create a free account to view solution
View Solution FreeMore Progression (Sequence and Series) Questions
The HM between 1/21 and − 1/5 is -...If a,b,c are in G.P. and A.M. between a,b, and b,c are respectively p and q, then (a / p) + (c / q) is equal to-...If the Standard Deviation of a variate is s, then the S.D. of 3x + 2 is:...Let Tr be the r th term of an AP, for r = 1, 2, 3....... if for some positive integers m, n we have Tm = and Tm = , then...Let $\displaystyle\sum_{k=1}^{n} a_k = \alpha n^2 + \beta n$. If $a_{10} = 59$ and $a_6 = 7a_1$, then $\alpha + \beta$ i...