Which of the following is not an arithmetic sequence? 1, 3, 5, 7, ... 4, 9, 14, 19, ... 3, 6, 12, 24, ... 10, 20, 30, 40, ... 3 Right! You found what is called a geometric sequence. The student got this item correct. Sorry, that's not right. Notice the common difference between each pair of numbers in the sequence you selected. That means that it IS an arithmetic sequence. Not sure what the problem is. Arithmetic