Loading...

There was an error loading the page.


Try to answer the following questions here:

  • What is this question used for?
  • What does this question assess?
  • What does the student have to do?
  • How is the question randomised?
  • Are there any implementation details that editors should be aware of?

History and Feedback

Comment

Checkpoint description

Describe what's changed since the last checkpoint.

Picture of Christian Lawson-Perfect

Christian Lawson-Perfect 2 years, 1 month ago

Gave some feedback: Ready to use

Picture of Christian Lawson-Perfect

Christian Lawson-Perfect 2 years, 1 month ago

Saved a checkpoint:

I've vastly rewritten the advice, and given the variables sensible names.

It would be good to have another version of this question where you fill in the table first.

Restore this checkpoint

Elliott Fletcher 2 years, 1 month ago

Published this.

Aiden McCall 2 years, 2 months ago

Saved a checkpoint:

I have edited the advice. I think the spacing/positioning could be done better but am not sure how to do this with the tables so they don't stretch when you move each part.

Restore this checkpoint

Aiden McCall 2 years, 2 months ago

Saved a checkpoint:

 The advice in this question is very hard to follow. I have an alternative method and am going to change the advice. In case my method is not preferred or wants to be reverted I have made a checkpoint here.

Restore this checkpoint

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Needs to be tested

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Has some problems

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Needs to be tested

Picture of Christian Lawson-Perfect

Christian Lawson-Perfect 2 years, 2 months ago

Also, note that I used "first differences" and "second differences" - I thnk Lauren also spotted that it's tricky to keep track of all the differences floating about.

Picture of Christian Lawson-Perfect

Christian Lawson-Perfect 2 years, 2 months ago

Gave some feedback: Has some problems

Picture of Christian Lawson-Perfect

Christian Lawson-Perfect 2 years, 2 months ago

Saved a checkpoint:

The layout of the advice is very hard to follow.

I would work this out by drawing up a table with rows for $n$, $a_n$, and first and second differences. 

For example,

$n$ 1 2 3 4
$a_n$ 15 22 33 48
First differences 7 11 15
Second differences 4 4

Because the second difference is $4$, I know that the coefficient of $x^2$ is $4/2 = 2$.

Then I can add a row for $a_n - 2n^2 = bn+c$:

$n$ 1 2 3 4
$a_n$ 15 22 33 48
$2n^2$ 2 8 18 32
$a_n-2n^2$ 13 14 15 16

So $bn+c = n+12$, and the formula for the whole sequence is $a_n = 2n^2+n+12$.

Sometimes, a good layout can save a lot of verbiage!

Restore this checkpoint

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Needs to be tested

Lauren Richards 2 years, 2 months ago

Gave some feedback: Has some problems

Lauren Richards 2 years, 2 months ago

  • So after you have found the difference between the sequential terms, and then found the difference between the differences, which you found in the question I did to be 8, it is not clear how you would decide to start the nth term off as 8/2n^2. I think you need to add in a line explaining your reasoning for this.
  • I don't think the first sentence reads very well. Maybe something more like "We first need to calculate the differences between the terms in the sequence.". and then for the second bit of writing "We can then calculate the differences of the term differences." I totally get that that is quite hard to word without being confusing. 
  • I think "original sequence" should probably be capitalised. 
  • In the advice, the second bit of writing that finishes with the word differences, is missing a full stop. You're also missing a comma at the end of "difference" near the end of the advice but I think this sentence should be re-worded anyway as it starts with "If", but then doesn't really end it like you would expect. I think it should be something like "We should first find the common difference.".
  • No fault of yours but it gets a little confusing with the amount of differences being mentioned, and I think when you refer to the "sequence of differences" you should have sequence of differences in brackets when you first make it to make it clear when you next refer to it. 
  • I think differences sequence should be capitalised.
  • At the end, you're calculating the difference between 2n and the sequence of differences but you haven't done that in the same way as you have done earlier in the question advice and I think you probably should do. 
  • One time I did the question, it said "Then we can find the difference between 1n and our sequence of differences" so I think you should make sure it just states "n" in this case. 
  • I think this is a good question, and tricky to make clear! 

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Needs to be tested

Vicky Hall 2 years, 2 months ago

Gave some feedback: Has some problems

Vicky Hall 2 years, 2 months ago

I would reword the question to say 'Find the formula for the $n$th term of the quadratic sequence'.

The advice is good but think the last part, where you find the constant, would look better if it were laid out like the previous part, so you show the student what the sequence $3n^2+3n$ looks like compared to the original sequence. You also need to remove the reference to part b).

Hannah Aldous 2 years, 2 months ago

Gave some feedback: Needs to be tested

Hannah Aldous 2 years, 2 months ago

Created this as a copy of Compute the partial sum of an arithmetic sequence.
Name Status Author Last Modified
Arithmetic sequences in an ice cream shop Ready to use Hannah Aldous 01/08/2017 13:41
Compute the partial sum of an arithmetic sequence Ready to use Hannah Aldous 01/08/2017 13:32
Finding the $n^{\text{th}}$ Term of a Quadratic Sequence Ready to use Hannah Aldous 01/08/2017 13:28
Identifying different types of sequences Ready to use Hannah Aldous 14/05/2019 14:52
Finding the formula for the $n^{\text{th}}$ term of linear sequences Ready to use Hannah Aldous 01/08/2017 13:40
Partial sum of an arithmetic sequence - birthday money Ready to use Hannah Aldous 01/08/2017 13:45
Find common difference in arithmetic sequences with gaps Ready to use Christian Lawson-Perfect 01/08/2017 13:56
Fill in the gaps in an arithmetic sequence Ready to use Christian Lawson-Perfect 01/08/2017 13:57
Write down and apply the formula for an arithmetic sequence. Ready to use Christian Lawson-Perfect 01/08/2017 13:57
Finding the Formula for the $n^{\text{th}}$ Term of Linear Sequences draft Chris Graham 20/07/2017 15:08
Inbbavathie's copy of Find common difference in arithmetic sequences with gaps draft Inbbavathie Ravi 24/07/2017 03:48
Find a particular term of a sequence using the given formula Ready to use Christian Lawson-Perfect 01/08/2017 13:31
Johan's copy of Write down and apply the formula for an arithmetic sequence. Has some problems Johan Maertens 02/08/2017 17:51
Finding the formula for the $n^{\text{th}}$ term of linear sequences draft steve kilgallon 19/11/2017 08:09
Compute the partial sum of an arithmetic sequence draft steve kilgallon 19/11/2017 08:11
Identifying different types of sequences draft Luis Hernandez 31/12/2018 01:38
Calcular la suma parcial de una sucesión aritmética Ready to use Luis Hernandez 14/01/2019 17:37
Identificando diferentes tipos de secuencias Ready to use Luis Hernandez 14/01/2019 13:19
Suma parcial de una secuencia aritmética - Cumpleaños Ready to use Luis Hernandez 14/01/2019 19:01
Encontrar la diferencia común en una Secuencia Aritmética Ready to use Luis Hernandez 14/01/2019 17:40
Encuentra un término particular de una secuencia usando la fórmula dada Ready to use Luis Hernandez 14/01/2019 17:48
Encontrar la fórmula para el término $n^{\text {th}}$ de una secuencia lineal Ready to use Luis Hernandez 14/01/2019 19:29
Simon's copy of Write down and apply the formula for an arithmetic sequence. draft Simon Thomas 25/02/2019 10:20
Simon's copy of Find common difference in arithmetic sequences with gaps draft Simon Thomas 25/02/2019 10:24
Simon's copy of Finding the formula for the $n^{\text{th}}$ term of linear sequences draft Simon Thomas 25/02/2019 10:30
Identifying different types of sequences draft Xiaodan Leng 10/07/2019 21:48
Write down and apply the formula for an arithmetic sequence. draft Xiaodan Leng 11/07/2019 01:48
Fill in the gaps in an arithmetic sequence draft Xiaodan Leng 11/07/2019 01:48
Find common difference in arithmetic sequences with gaps draft Xiaodan Leng 11/07/2019 01:49
Compute the partial sum of an arithmetic sequence draft Xiaodan Leng 11/07/2019 01:51
Partial sum of an arithmetic sequence - birthday money draft Xiaodan Leng 11/07/2019 01:54
Arithmetic sequences in an ice cream shop draft Xiaodan Leng 11/07/2019 01:55
Finding the formula for the $n^{\text{th}}$ term of linear sequences draft Xiaodan Leng 11/07/2019 01:55
Find a particular term of a sequence using the given formula draft Xiaodan Leng 11/07/2019 01:56
Finding the $n^{\text{th}}$ Term of a Quadratic Sequence draft Xiaodan Leng 11/07/2019 01:57

Give any introductory information the student needs.

No variables have been defined in this question.

(a number)

Numbers between and (inclusive) with step size
A random number between and (inclusive) with step size

(text string)

(numbers)

(text strings)

This variable is an HTML node. HTML nodes can not be relied upon to work correctly when resuming a session - for example, attached event callbacks will be lost, and mathematical notation will likely also break.

If this causes problems, try to create HTML nodes where you use them in content areas, instead of storing them in variables.

Describe what this variable represents, and list any assumptions made about its value.

Name Type Generated Value

Error in variable testing condition

There's an error in the condition you specified in the Variable testing tab. Variable values can't be generated until it's fixed.

Error:

for seconds

Running for ...

No parts have been defined in this question.

Select a part to edit.

Ask the student a question, and give any hints about how they should answer this part.

The correct answer is an equation. Use the accuracy tab to generate variable values satisfying this equation so it can be marked accurately.

Advanced settings


Checking accuracy

Define the range of points over which the student's answer will be compared with the correct answer, and the method used to compare them.

Variable value generators

Give expressions which produce values for each of the variables in the expected answer. Leave blank to pick a random value from the range defined above, following the inferred type of the variable.

Pattern restriction


Variables


String restrictions

Advanced settings




Advanced settings


Advanced settings



Advanced settings



Advanced settings



Answers
Choices
Both choices and answers must be defined for this part.

Advanced settings




Help with this part type


Base marking algorithm

                                        
Custom marking algorithm


Test that the marking algorithm works

Check that the marking algorithm works with different sets of variables and student answers using the interface below.

Create unit tests to save expected results and to document how the algorithm should work.

There's an error which means the marking algorithm can't run:


                                    
Name Value

Note
Value Feedback

Click on a note's name to show or hide it. Only shown notes will be included when you create a unit test.


Unit tests

No unit tests have been defined. Enter an answer above, select one or more notes, and click the "Create a unit test" button.

The following tests check that the question is behaving as desired.

This test has not been run yet This test produces the expected output This test does not produce the expected output

This test is not currently producing the expected result. Fix the marking algorithm to produce the expected results detailed below or, if this test is out of date, update the test to accept the current values.

One or more notes in this test are no longer defined. If these notes are no longer needed, you should delete this test.

Name Value

Note Value Feedback
This note produces the expected output Current:
Expected:

This test has not yet been run.

When you need to change the way this part works beyond the available options, you can write JavaScript code to be executed at the times described below.

Run this script the built-in script.

This script runs after the built-in script.

To account for errors made by the student in earlier calculations, replace question variables with answers to earlier parts.

In order to create a variable replacement, you must define at least one variable and one other part.

Variable Answer to use Must be answered?

The variable replacements you've chosen will cause the following variables to be regenerated each time the student submits an answer to this part:

These variables have some random elements, which means they're not guaranteed to have the same value each time the student submits an answer. You should define new variables to store the random elements, so that they remain the same each time this part is marked.

More information about this problem

to

Parts

Give a worked solution to the whole question.

Extensions

Rulesets

Functions

Preamble

This script will run after the question's variable have been generated but before the HTML is attached.
Apply styling rules to the question's content.

This question is used in the following exam: