You are Here: Home >< Maths

C1 Sequence, I have the written solutions but don't understand one of the solutions. Watch

Announcements
1. I have attached an image of both the question and written solution. It is part C, which I have circled.

I get that there are 52 terms because it is for the second year (52 days). I also get that it increases by 11 each time, because the commission in the second year is £11 per week.

HOwever, I don't get why after the final week and final term (where it says 52), why there is a "x 11" after that, and I don't get why it is multiplied by 11.

Please can someone explain to me why the 52 is multiplied by 11?

Any help would be greatly appreciated, Thanks!

2. (Original post by blobbybill)
Please can someone explain to me why the 52 is multiplied by 11?

Any help would be greatly appreciated, Thanks!
Is this the line following "commission for year 1 policies +...". If so,

The numbers in brackets are (11+22+33+....
i.e. (1x11 + 2x11 + 3x11 +... + 52x11)

They put it as 52x11, rather than work out the actual value of 572.
3. (Original post by ghostwalker)
Is this the line following "commission for year 1 policies +...". If so,

The numbers in brackets are (11+22+33+....
i.e. (1x11 + 2x11 + 3x11 +... + 52x11)

They put it as 52x11, rather than work out the actual value of 572.
Ah ok, so if they put it as 572, that would be the final term?

Also, in the equation of Sn = n/2 [2a + (n-1)d], the solutions show n to be n=52. How would you know whether n would be 52 or 572 when substituting it into the equation? I can see its 52 now, but if it came up in an exam, i wouldnt know whether to use 52 (because 52 weeks in year), or 572 (because its the value of the final term)?

Thanks!
4. (Original post by blobbybill)
Ah ok, so if they put it as 572, that would be the final term?
Yes.

Also, in the equation of Sn = n/2 [2a + (n-1)d], the solutions show n to be n=52. How would you know whether n would be 52 or 572 when substituting it into the equation? I can see its 52 now, but if it came up in an exam, i wouldnt know whether to use 52 (because 52 weeks in year), or 572 (because its the value of the final term)?

Thanks!
In the formula for Sn, "n" is the number of terms in the arithmetic progression, hence 52, not 572.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: September 30, 2016
Today on TSR

Oxbridge

Even more elitist than everyone thought?

Physically ill after being cheated on

Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants

Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.