Question

A progression has a first term of 12 and a fifth term of 18.

Find the 13th term if the progression is geometric.

Answer 1

xr xr xr xr
12 ---> a2--->a3--->a4--->18
So 12(r^4) =18
\[r=\sqrt[4]{1.5}\]
T(13) = 12r^(13-1) 12r^12...

Answer 2

sorry
T(13) = 12r^(13-1) =12r^12 = 12[(1.5)^(1/4)]^12 = 12(1.5)^3 = 40.5...

Answer 3

Hmm.. Do you understand?

Answer 4

Ok. THank you. Yes, I do. But i got 40.64

Answer 5

can you show your workings?

Answer 6

18=12r^4
1.5=r^4
1.5^1/4=r
r= 1.107

An= 12(1.107)^12
An= 40.6

Answer 7

it's because you round the number for r...