pls can you explain how to find the nth number for 1,6.11.21.31, thanks jackie?

Answer 1

As with most finite sequences, it's impossible to tell for sure. However, here are some relatively simply answers:

The sequence looks like: {0,5,10,20,30,...} + {1}

So, the simplest answers will likely be of the form a(n) = a(n-1) f(n) + 1 where a(n) is the nth term and is defined recursively.

An example of this is:

a(n=1) = 1
a(n>1) = a(n-1) + 5*roundup((n-1)/2)

So, from the above:

a(1) = 1
a(2) = a(1)+5*roundup((2-1)/2) = 1+5*roundup(1/2) = 1+5*1 = 6
a(3) = a(2)+5*roundup((3-1)/2) = 6+5*roundup(2/2) = 6+5*1 = 6

etc.

This would give you the following for the next two in the sequence: 46 and 61.
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On the other hand, another possibility is that the next two in the sequence go like: 51 and 71. One could achieve this by doing the following.

Note that the difference sequence can be written as:

{0,5,5,10,10,20,20} + {1}

Now, the first part looks like:

{5,5,10,10,20,20} but offset by 1 place.

This, in turn, looks like:

5*{1,1,2,2,4,4} which is 5*{2^0,2^0,2^1,2^1,2^2,2^2}

or 5*{2^rounddown((m-1)/2)}

because this will give: (m=1,2^0), (m=2,2^0), (m=3,2^1) etc

Now, we have to translate m to n: Since we shifted the sequence left, this would be:

m = n - 1

So, the final sequence looks like:

a(1) = 1
a(n>1) = a(n-1) + 5*2^rounddown(n/2-1)

Both the sequence and the difference are nonlinear which makes any representation - whether absolute or recursive - nonlinear, as well.

Answer 2

i think the next number is 46? i got that answer by adding 15 to 31. There's an interval first add 5 to the first two numbers. Then add 10 to the next two.

n+5+5+10+10+15+15+20+20....

Answer 3

did u take this off an IQ test? and is it suppose to be 1, 6, 11, 21, 31? You just look for the pattern and make a simple equation for it. Such as 2, 4, 6, 8, 10.... repeating by two's obviously... so the equation is 2n, if you want to know what the 38th number is in the sequence just put 38 in for n.

Answer 4

46

Answer 5

the "nth" number? what's an "nth" number?

Answer 6

1,6,11,21,31,46,61,81,101
lol