AQA AS Maths Further Pure 1 Question Watch

Firefox23
Badges: 8
Rep:
?
#1
Report Thread starter 4 years ago
#1
Hi, I am struggling to understand the highlighted question. I thought you would just take the sum of the squares of the odd numbers between up 100 away form the sum up to 200, but the mark scheme says to do sum up to 100 - sum up to 50
Attached files
0
reply
JerzyDudek
Badges: 11
Rep:
?
#2
Report 4 years ago
#2
Can you post the mark scheme?

(Original post by Firefox23)
I thought you would just take the sum of the squares of the odd numbers between up 100 away form the sum up to 200
That's what I would do as well.
0
reply
AranAlpaca
Badges: 0
Rep:
?
#3
Report 4 years ago
#3
Does the mark scheme say to do the sum for all values of r=100 minus the sum of the values up to r=50? If r=100 or 50, what would 2r-1 equal?
0
reply
Gymnast
Badges: 1
Rep:
?
#4
Report 4 years ago
#4
Is there a tread for the FP1 exam tomorrow
0
reply
JerzyDudek
Badges: 11
Rep:
?
#5
Report 4 years ago
#5
(Original post by ktalexander)
Does the mark scheme say to do the sum for all values of r=100 minus the sum of the values up to r=50? If r=100 or 50, what would 2r-1 equal?
Thank you, you are right, I somehow missed that.

To OP: Just look at the first and the last odd numbers in the interval because 100 and 200 are even and find corresponding r's. Hope I don't do such stupid things tomorrow
0
reply
Firefox23
Badges: 8
Rep:
?
#6
Report Thread starter 4 years ago
#6
Here's the mark scheme
Attached files
0
reply
Firefox23
Badges: 8
Rep:
?
#7
Report Thread starter 4 years ago
#7
(Original post by JerzyDudek)
Thank you, you are right, I somehow missed that.

To OP: Just look at the first and the last odd numbers in the interval because 100 and 200 are even and find corresponding r's. Hope I don't do such stupid things tomorrow
Sorry I don't quite understand what you mean, so you mean 101 being the first and 199 being the last?
0
reply
JerzyDudek
Badges: 11
Rep:
?
#8
Report 4 years ago
#8
(Original post by Firefox23)
Sorry I don't quite understand what you mean, so you mean 101 being the first and 199 being the last?
Yes, because the list is 101, 103, 104...199 so it doesn't matter if it's from 100 to 200 or from 101 to 199 in this case. However if you want to find the limits for r you need to equate the actual limit to 2r-1. For example, 101 = 2r - 1 gives r = 51 but 100 = 2r + 1 won't give you an integer. Do the same for the upper limit.

Then remember that  \displaystyle\sum^a_b = \displaystyle\sum^a_0 - \displaystyle\sum^{b-1}_0 .
0
reply
Firefox23
Badges: 8
Rep:
?
#9
Report Thread starter 4 years ago
#9
(Original post by JerzyDudek)
Yes, because the list is 101, 103, 104...199 so it doesn't matter if it's from 100 to 200 or from 101 to 199 in this case. However if you want to find the limits for r you need to equate the actual limit to 2r-1. For example, 101 = 2r - 1 gives r = 51 but 100 = 2r + 1 won't give you an integer. Do the same for the upper limit.

Then remember that  \displaystyle\sum^a_b = \displaystyle\sum^a_0 - \displaystyle\sum^{b-1}_0 .
Oh I understand so would that be the case for any question like that? Like if they said between 300 and 400 I'd use 150 and 200?
0
reply
JerzyDudek
Badges: 11
Rep:
?
#10
Report 4 years ago
#10
(Original post by Firefox23)
Oh I understand so would that be the case for any question like that? Like if they said between 300 and 400 I'd use 150 and 200?
Yes, as long as it's in the form 2r - 1. More generally make whatever you are summing equal to the first and last terms and find r limits. And then simply don't forget the rule in the above post.
0
reply
Firefox23
Badges: 8
Rep:
?
#11
Report Thread starter 4 years ago
#11
(Original post by JerzyDudek)
Yes, as long as it's in the form 2r - 1. More generally make whatever you are summing equal to the first and last terms and find r limits. And then simply don't forget the rule in the above post.
Ok thanks, 1 more question, with that the question was actually asking for the sum of the squares so (2r-1)^2, why didn't I make that equal to 100 but left out the squared and just used 2r-1?
0
reply
jkrolling12
Badges: 0
Rep:
?
#12
Report 4 years ago
#12
How did everyone find it?
0
reply
Gymnast
Badges: 1
Rep:
?
#13
Report 4 years ago
#13
(Original post by jkrolling12)
How did everyone find it?
Alright ish, it could have been so much worse but it could also have been better, so to be honest I am a bit unsure as to what I will get in that paper
0
reply
jkrolling12
Badges: 0
Rep:
?
#14
Report 4 years ago
#14
(Original post by Gymnast)
Alright ish, it could have been so much worse but it could also have been better, so to be honest I am a bit unsure as to what I will get in that paper
same tbh, were there any questions you couldnt do?
0
reply
Firefox23
Badges: 8
Rep:
?
#15
Report Thread starter 4 years ago
#15
(Original post by jkrolling12)
same tbh, were there any questions you couldnt do?
Yeah I'm the same, I couldn't so the last question and I'm not sure about the general solutions one part b. I didn't have much time to check through either so I may have made some other little mistakes throughout the paper
0
reply
jkrolling12
Badges: 0
Rep:
?
#16
Report 4 years ago
#16
(Original post by Firefox23)
Yeah I'm the same, I couldn't so the last question and I'm not sure about the general solutions one part b. I didn't have much time to check through either so I may have made some other little mistakes throughout the paper
Same grade boundaries as last year do you think?
0
reply
Gymnast
Badges: 1
Rep:
?
#17
Report 4 years ago
#17
(Original post by Firefox23)
Yeah I'm the same, I couldn't so the last question and I'm not sure about the general solutions one part b. I didn't have much time to check through either so I may have made some other little mistakes throughout the paper
Struggled on exactly same questions, and I struggles for time as well but no point in worrying now just need to move on still got three exams left ( mechanics, decision one and two ) hoping they go well
0
reply
Firefox23
Badges: 8
Rep:
?
#18
Report Thread starter 4 years ago
#18
(Original post by jkrolling12)
Same grade boundaries as last year do you think?
I really hope so! I thjnk this years wasn't technically as hard but it was harder in the hard topics if that makes sense
0
reply
Gymnast
Badges: 1
Rep:
?
#19
Report 4 years ago
#19
(Original post by Firefox23)
I really hope so! I thjnk this years wasn't technically as hard but it was harder in the hard topics if that makes sense
I hope so too! Think they may be a tad higher but not much, talking like 2/3 marks higher
0
reply
Firefox23
Badges: 8
Rep:
?
#20
Report Thread starter 4 years ago
#20
(Original post by Gymnast)
I hope so too! Think they may be a tad higher but not much, talking like 2/3 marks higher
Yeah I think most people will have made a few mistakes and as a result will have messed up whole questions and a few marks throughout just for simple errors so definitely low 60s hopefully even less
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

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.

Personalise

University open days

  • Edge Hill University
    Undergraduate and Postgraduate - Campus Tour Undergraduate
    Mon, 18 Feb '19
  • University of the Arts London
    MA Innovation Management Open Day Postgraduate
    Mon, 18 Feb '19
  • University of Roehampton
    Department of Media, Culture and Language; School of Education; Business School Undergraduate
    Tue, 19 Feb '19

Do you give blood?

Yes (53)
8.75%
I used to but I don't now (16)
2.64%
No, but I want to start (222)
36.63%
No, I am unable to (140)
23.1%
No, I chose not to (175)
28.88%

Watched Threads

View All