09 Aug 2008

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

The series is -

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

What's the next number in above series?

bayazidahmed

Branch Unspecified
10 years ago
12285

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

Branch Unspecified
10 years ago
I am too busy to post the explanation now. I'll leave it for another 24 hours.

mahul

Branch Unspecified
10 years ago
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

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