Posted by Schuyler on .
What is the sum of a 12term arithmetic sequence where the last term is 13 and the common difference is 10?

Alg 2 
Raymond,
Schuyler, the sum of the 12 term aritmetic progression is 816

Alg 2 
Raymond,
Schuyler, in order to solve your problem I had to turn it around (Gloria Estefan?). You said the last term was 13...I made it the first term. You said the common difference was a 10...I made it a +10.
Now I had to find the last term so I used this formula: L=a+(n1)d so 13+(121)10
L=123
Then I used this formula:
Sn=n/2(a+L)
Sn=12/2(13+123)
Sn=6 Times 136
Sn=816