Find the next number: 12,12,18,45,180,1170,?

[The_Big_K]

The series is -

12,12,18,45,180,1170,?

What's the next number in above series?

[bayazidahmed]

12285

Shall I give the solution or wait for some one else to rattle their brain and figure it out?

[The_Big_K]

Originally Posted by bayazidahmed

12285

Shall I give the solution or wait for some one else to rattle their brain and figure it out?

Wait!

If no one replies in next 24 hours, post the explanation!

[bayazidahmed]

I am too busy to post the explanation now. I'll leave it for another 24 hours.

[mahul]

Yep, my answer matches with that of bayazidahmed, 12285.

Here's the solution:

Lets name the general term of the sequence T(n)

The sequence (say R(n)) where R(n)=T(n+1)/T(n)
is 1,1.5,2.5,4,6.5...

The sequnece (say S(n)) where S(n)=R(n+1)-R(n)
is 0.5,1,1.5,2.5....


Thus S(n) can be thought of a fibonacci style sequence where S(n)=S(n-1)+S(n-2)
Considering this relation, the next term in S(n) would be 1.5+2.5=4

Considering this, the next trem in R(n) would be 6.5+4=10.5

Thus the next term in T(n)=1170*10.5 = 12285