# Thread: Geometric progression

1. ## Geometric progression

P = a1 + a4 + a7 + a10..... + a34
Q = a2 + a5 + a8 + a11 .... + a35

how many terms in each one?

The answer is 12

* i came to conclusion that the q for each one is q3

2. ## Re: Geometric progression

It is certainly true that both 1, 4, 7, ..., 34, and 2, 5, 8, ..., 35 are arithmetic sequences with common difference 3 so, since 34= 1+ 3(11), and 35= 2+ 3(11), each has 11+ 1= 12 terms. I have no idea what "the $\displaystyle q$ for each one is $\displaystyle q^3$" means.

3. ## Re: Geometric progression

Originally Posted by HallsofIvy
It is certainly true that both 1, 4, 7, ..., 34, and 2, 5, 8, ..., 35 are arithmetic sequences with common difference 3 so, since 34= 1+ 3(11), and 35= 2+ 3(11), each has 11+ 1= 12 terms. I have no idea what "the $\displaystyle q$ for each one is $\displaystyle q^3$" means.
What's the 11 for?

4. ## Re: Geometric progression

Originally Posted by Mustafashama
What's the 11 for?
$P=\{a\times a^n:n=0,1,2,3,4,5,5,6,7,8,9,10,11\}$
That is twelve values of $n$.