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Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@Kaustubh Katdare • 04 Aug, 2008
The series is -

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

What's the next number in above series?
@bayazidahmed • 07 Aug, 2008 12285

Shall I give the solution or wait for some one else to rattle their brain and figure it out?
@Kaustubh Katdare • 07 Aug, 2008
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 • 09 Aug, 2008 I am too busy to post the explanation now. I'll leave it for another 24 hours.
@mahul • 09 Aug, 2008 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
7.5k views

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