You are Here: Home >< Maths

# c1 question Watch

1. Evaluate

30 r=10∑ (7 + 2r)

30 is above the sigma sign and r=10 is below
2. split it so it's like this;

3. (Original post by NotNotBatman)
split it so it's like this;

can you explain it further and what you'd do?
the mark scheme uses n/2 ( a + L) i believe which isnt what we've learnt
4. since when is this c1??, what board are you doing ?
5. (Original post by Mina_)
can you explain it further and what you'd do?
the mark scheme uses n/2 ( a + L) i believe which isnt what we've learnt
where a is the first term and l is the last term, it's a standard formula which you should learn.

So if you have to sum from to then that's

,

but this formula uses the first term, so you have to realise that the sum from to is the same as summing from to subtract the sum form to

because

and

and notice when you subtract them you're left with the summation form to
which is what you're asked for, so apply the summation formula remembering a is the first term (the number at the bottom) and l is the last term (the number at the top).
6. (Original post by NotNotBatman)
where a is the first term and l is the last term, it's a standard formula which you should learn.

So if you have to sum from to then that's

,

but this formula uses the first term, so you have to realise that the sum from to is the same as summing from to subtract the sum form to

because

and

and notice when you subtract them you're left with the summation form to
which is what you're asked for, so apply the summation formula remembering a is the first term (the number at the bottom) and l is the last term (the number at the top).
Thank you!
7. (Original post by Science_help)
since when is this c1??, what board are you doing ?
Edexcel, haha this is from the solomon papers which is typically harder
8. Just sub in 10 and 30, your 'n' value is 30-10+1= 21, so 21/2(a+L)
9. (Original post by Mina_)
Edexcel, haha this is from the solomon papers which is typically harder
ahh adexcel, makes sense, in aqa we have this topic in c2, similar to how circle geometry is on c2 for edexcel, whereas its c1 for aqa?

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: May 8, 2016
Today on TSR

### Does race play a role in Oxbridge admissions?

Or does it play no part?

### The worst opinion about food you'll ever hear

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

## 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.