IBPS
Government Jobs Exams
Numerical Ability
Sequence and Series
Find the 87th number in the series 2, 10, 26, 50
a) 160
b) 260
c) 60
d) None
Read Solution (Total 3)
-
- nth term is 2 + (8 + 16 + 24 + ... (n-1) terms )
=> nth term = 2 + [ (n-1)(2*8 + 8n - 16)/2 ]
= 2 + 4n(n-1)
= 4n^2 - 4n + 2
=> 87th term = 4*87^2 - 4*87 + 2 = 29930 - 11 years agoHelpfull: Yes(1) No(3)
- ans is none.. bcoz ans is 29930
- 11 years agoHelpfull: Yes(0) No(3)
- 2 = 1^2 + 1
10 = 3^2 +1
26 = 5^2 + 1
50 = 7^2 + 1
Now,
1,3, 5, 7 ...... forms a AP series with common difference 2.
So, we will find T87 firs through Ap.
Tn = a +(n-1)*d
Tn = 1 + (87 -1) *2 = 1 + 86 *2 = 173.
Now,
87th term = 1732 + 1 = 29929 + 1 = 29930. - 7 years agoHelpfull: Yes(0) No(0)
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