arithmetic sequence

Arithmetic Sequence

In an Arithmetic Sequence the difference between one term and the next is a constant. In other words, we just add the same value each time ... infinitely.

In General we could write an arithmetic sequence like this: {a, a+d, a+2d, a+3d, ... }


  • a is the first term, and
  • d is the difference between the terms (called the "common difference")


We can write an Arithmetic Sequence as a rule: xn = a + d(n-1)

Summing an Arithmetic Series 

To sum up the terms of this arithmetic sequence:

a + (a+d) + (a+2d) + (a+3d) + ...

use this formula: 

see more :


Given a 100 terms of arithmetic sequence, first term is  3, and the difference is 4, a new term is inserted between each tow terms and a new arithmetic sequence is received. What is the sum of terms of the new sequence?

2 People tried to answer this question





very good :)

you should sum up the terms of the new arithmetic sequence (not the given sequence).

think about the diffrence of the new sequence.

the number of terms in the new sequence is not 200 !!!

1.  Sarboukh Helana (24.06.2017 pm 09.40.13)
arithmetic sequence


You chose a subject that is very interesting and challenging for students, and requires high level of thinking.

To present the subject, you have used number of methods to simplify it, such as a short explanation, and a formula for calculating the exercise and a link to a lecture at BLLOSOM , all of these methods could help  students to study the subject by themselves, help them understand the solution, and  enrich the information they already have, especially the lecture that present a lot of information and few examples.

For improvement, the subject could be presented in a more creative and attractive way. In addition, I would suggest presenting the meaning of the letters in the formula (k,n…)  and a simple example, rather than confirming that it is presented in the lecture in the link.


Thank you and good luck.






2.  ginzburg tamar (07.11.2018 pm 01.00.26)
Question Evaluation


Overall, this is a well written question that starts with giving the needed information to answer the presented question.  It also gives a link to a relevant lesson that gives further explanation, which can help the student learn the subject better by repetition.  Unfortunately, the video that was included in the question did not work.  In order to improve, I would suggest explaining why the answer that was chosen is the correct one by showing the numbers plugged into the formula.  Overall, I would say this question teaches the subject of arithmetic sequence well.


History of edits
Edited BY: ali samhat Edit Date: 2017-05-29 17:42:18
Edited BY: ali samhat Edit Date: 2017-05-29 17:41:43
Edited BY: ali samhat Edit Date: 2017-05-29 17:39:43
Edited BY: ali samhat Edit Date: 2017-05-29 17:31:12
Edited BY: ali samhat Edit Date: 2017-05-29 17:26:47
Edited BY: ali samhat Edit Date: 2017-05-29 17:24:10
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