.
Let me help to you both.
The sequence is
day eat per day cumulative sum (same as TOTAL)
1 3 3
2 3 6
3 3 9
4 3 12
. . . . . . . . . . . . . . . . . . . . . . .
The TOTAL is the Arithmetic progression with the first term = 3 and the common difference d = 3.
Solved.
On arithmetic progression see the introductory lessons
- Arithmetic progressions
- The proofs of the formulas for arithmetic progressions
- Problems on arithmetic progressions
- Word problems on arithmetic progressions
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".