I am stuck on a problem. Can Somebody tell me what the next number is in the pattern 9,11,15,20,25?
Hmm. Normally these kinds of questions involve a sequence where the terms differ by a steadily increasing or decreasing amount. Here the differences are
2,4,5,5
One way to continue the sequence would be to have a symmetric set of differences. In that case, we could continue the differences with
2,4,5,5,4,2 making the sequence continue on as
9,11,15,20,25,29,31
Not very satisfactory; maybe others can devise a more useful solution.
Naturally, there are any number of polynomials which will fit the data:
p(n) = -1/6 (n^3 - 12n^2 + 17n - 60)
will make the sequence continue
9,11,15,20,25,29,31,30,25,15