Logical Reasoning - Number Series - Discussion

General form is X(n+1) = (X (n)*n) - (n+1) ). Where X(n) is the term number in the series, X (n+1) is the subsequent term and n is the element position aka as index.

All algebraic terms will always represent integer values.

X(n); n(X (n)*n)-(n+1)) = X(n+1).

X(1) = 8; n = 1((8)*(1))-(2)) = 6.

X(2) = 6; n = 2((6)*(2))-(3)) = 9.

X(3) = 9; n = 3((9)*(3))-(4)) = 23.

X(4) = 23; n = 4((23)*(4))-(5)) = 87.

X(5) = 87; n = 5((87)*(5))-(6)) = 429.

Therefore.

X(6) = 429; n = 6((429)*(6))-(7)) = 2567.

@Stefy,

Although we can indeed use the logic of adding the 1st 2nd 3rd and then the 3rd 4th 5th, through this method there is no way to derive the 2nd number, and the others as well,

Generally, a sequence series has to be applied so that you can find n and n +1 using the same formula. You shouldn't have to need to use n, n+1, n+2 to find n+3.

Hope this Helped! (To all the others who chance across this forum as well).

You can understand this problem by understanding the relation between 9, 23 as shown in the solution 9'-3-4=23, and later you check the remaining numbers by using this method.

If it suitable for every number before 9 then you can do this with 87.

Very confusing. I've got this solution adding the first 3 numbers (23)and then adding the third, fourth and fifth together
8, 6, 9, 23, 87

8+6+9 = 23.
9+23+87 = 128.

Can anybody explain why this solution is not correct?

@ALL.

As per my knowledge, this will go like.
a will start from 1 and increase to 1 in next , b start from 2 and increase 1.
8 x a - b = 6,
6 x (a++) - (b++),
9 x (a++) - (b++),
23 x (a++) - (b++),
87 x (a++) - (b++).

Given pro having 8, 6, 9, 23, 87.

We have to do,

8*1 = 8-2 = 6,(8 is the given no, it is in 1 place so 8*1=8 we want next no in the given series we have to subtract 8-2=6).

We follow this method remains all.

Then where the 8 come from.

Here. 8 x 1 - 2 = 6.

6 x 2 - 3 = 9.

9 x 3 - 4 = 23.

23 x 4 - 5 = 87.

87 x 5 - 6 = 429.

Then what is the logic for "8".

6 is not the first number here. 8 is the first number.

Simple dear how can see,

8*1 = 8-2 --> 6 1st num.
6*2 = 12-3 --> 9 2nd num.
9*3 = 27-4 --> 23 3rd num.
23*4 = 92-5 --> 87 4th num.
87*5 = 435-6 --> 429 Answer.

One said that by adding the first 3 no's we can get 4th and adding next 3 no's we get 6th but it's wrong. Because if we follow this how we can get 2nd and 3rd no's.

It very complicated but very easy if understand thanks to the all persons commented on this, which make me understand so nicely and perfectly.