Answer:
10 terms. I think you should check the explanation :)
Explanation:
0.4 + 1.2 + 3.6 + ... + 7,873.2?
So I figured that you have to multiply the terms by three to get the next term.
0.4 * 3 = 1.2
1.2 * 3 = 3.6
But, I know it will takes us a really long time to get to 7,873.2, so what I will do is jump 3 sequences.
So if I multiply by 3 to get the next term, I'll multiply by 9 to get the next two terms because 3 * 3 is 9.
So to jump three times, I will multiply by 27 to get the next three terms because 3 * 3 * 3 is 27.
0.4 + 1.2 + 3.6 + ...
3.6 * 27 = 97.2
0.4 + 1.2 + 3.6 + ..., ..., 97.2, ...
97.2 * 27 = 2624.4
0.4 + 1.2 + 3.6 + ..., ..., 97.2, ..., ..., 2624.4, ...
Since we are getting close, I'm going to go back to multiply by 3.
2624.3 * 3 = 7873.2
0.4 + 1.2 + 3.6 + ..., ..., 97.2, ..., ..., 2624.4, 7873.2
Now that we have reached 7873.2, we will now count the terms (count the sets of three dots as terms too).
There are 10 terms in the geometric sequence.