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Logical Reasoning
Number Series
What is 87th term in series:
2.10.26.50?
ans-3741
Read Solution (Total 5)
-
- 2=1^2+1
10=3^2+1
26=5^2+1
..........
here ,1,3,5,7...... are odd numbers so by using An=a+(n-1)d
we can find the A87 th term for odd no. series..
A87=1+(87-1)x 2= 173
so ,the 87th term will be...
173^2+1=29930
ans: 29930 - 9 years agoHelpfull: Yes(20) No(3)
- as per the given series
Tn=T(n-1) +8*(n-1)
T87= T86+ 8*86
T87=2+8*(1+2+3............86)
T87= 2+8*(86*87/2)
T87=2+3741
T87=3743
- 9 years agoHelpfull: Yes(7) No(5)
- Consider the AP 0,8,16,24,,...........87th term is 688
a = 0
d=8
t87 = 87/2 ( 2(0)+(86)8) = 29928
as series starts from 2
add 2
answer is 29928 + 2 = 29930 - 6 years agoHelpfull: Yes(2) No(0)
- ans is 2066
- 8 years agoHelpfull: Yes(0) No(1)
- -->The difference b/w each num= Multiples of 8.
The nth term of the main series can be expressed as :
2 + sum of the series 8, 16, 32… till (n-1) terms
2 = 2+0
10 = 2+ 8
26 = 2 + 24 = 2 + (8 +16)
50 = 2 + 48 = 2 + (8 + 16 + 24)
.
..
nth term = 2 + (8+16+24+ ...+ till (n-1))
Therefore, the sum of 8, 16, 32… till (n-1) using the formula for the sum of an arithmetic progression will be
S=n−12[16+(n−2)8]
This simplifies as,
4n(n−1)
Thus the general term of the main series will be,
Tn=2+4n(n−1)
.
.
Thus the 87th term is
T87=2+4×87×86
T87=29930 - 6 years agoHelpfull: Yes(0) No(0)
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