- #1
Lasher
- 6
- 0
Homework Statement
In an arithmetic progression, the sum of the first 10 terms is the same as the sum of the next 5 terms. Given that the first term is 12, find the sum of the first 15 terms.
2.
The only one I could think of is
S= n/2 (2a+(n-1)d)
3.
I've tried solving it, but failed. I guess this is due to lack of experience, as I missed the topic.