As.1997
Badges: 16
Rep:
?
#1
Report Thread starter 1 year ago
#1
Please refer to the attachment. The answer is A. My approach (below)was to use test each answer option. Is there a quick way to do this? Is it obvious that it is 10?
If R=10, it leaves 38 for D, C and E.
R = 10
D = 17
C = 15
E = 6
This works, but if I tested the other options before 10. This question would have taken way to long. Is there any quick way to identify that 10 is the right answer?
Attached files
Last edited by As.1997; 1 year ago
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#2
Report 1 year ago
#2
largest difference have to be with best subject and worst subject. so we have
d = e + 11
and we know
d - c = 2
2 is the minimum, so r - e must be more than 3.

We should have:
e
r = e + x (x >= 3)
c = e+ 9
d = e +11
total = 4*e + 20 + x = 48.

obviously, 4*e, 20 and 48 is divisible by 4, so x is also divisible by 4
which leave us with x = 4, 8 or larger.
Now you try and see x = 4 give r = 10 is an answer.
8 give a smaller answer than what is available (it gives 9) so anything bigger than 8 can be rejected.
0
reply
joetr
Badges: 10
Rep:
?
#3
Report 1 year ago
#3
(Original post by Arctic Kitten)
largest difference have to be with best subject and worst subject. so we have
d = e + 11
and we know
d - c = 2
2 is the minimum, so r - e must be more than 3.

We should have:
e
r = e + x (x >= 3)
c = e+ 9
d = e +11
total = 4*e + 20 + x = 48.

obviously, 4*e, 20 and 48 is divisible by 4, so x is also divisible by 4
which leave us with x = 4, 8 or larger.
Now you try and see x = 4 give r = 10 is an answer.
8 give a smaller answer than what is available (it gives 9) so anything bigger than 8 can be rejected.
it says d and c were his two best sections, not d was his best section, so surely d could be plus or minus c as we don't know whether c or d is the best section? It ends up making 4e + x + 24 = 48 (24 divisible by four)
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#4
Report 1 year ago
#4
(Original post by joetr)
it says d and c were his two best sections, not d was his best section, so surely d could be plus or minus c as we don't know whether c or d is the best section? It ends up making 4e + x + 24 = 48 (24 divisible by four)
(Original post by Arctic Kitten)
largest difference have to be with best subject and worst subject
so the best subject has to be d
(because if c > d, then c - e > d - e, so largest difference won't be d - e, but c - e)
2
reply
joetr
Badges: 10
Rep:
?
#5
Report 1 year ago
#5
(Original post by Arctic Kitten)
so the best subject has to be d
(because if c > d, then c - e > d - e, so largest difference won't be d - e, but c - e)
Oh I see, that makes sense! Sorry for misreading
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#6
Report 1 year ago
#6
(Original post by joetr)
Oh I see, that makes sense! Sorry for misreading
No problem! Are you doing TSA past papers?
0
reply
As.1997
Badges: 16
Rep:
?
#7
Report Thread starter 1 year ago
#7
(Original post by Arctic Kitten)
largest difference have to be with best subject and worst subject. so we have
d = e + 11
and we know
d - c = 2
2 is the minimum, so r - e must be more than 3.

We should have:
e
r = e + x (x >= 3)
c = e+ 9
d = e +11
total = 4*e + 20 + x = 48.

obviously, 4*e, 20 and 48 is divisible by 4, so x is also divisible by 4
which leave us with x = 4, 8 or larger.
Now you try and see x = 4 give r = 10 is an answer.
8 give a smaller answer than what is available (it gives 9) so anything bigger than 8 can be rejected.
I’m stuck with 4e+20+x=48
Simplifying:
e+(x/4)=7
Since x>=3
x=4, 8, 12 or larger
If x=4, e=6
Therefore R=10

But if x=8, e=5 therefore R=13 which is also an option.
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#8
Report 1 year ago
#8
(Original post by As.1997)
I’m stuck with 4e+20+x=48
Simplifying:
e+(x/4)=7
Since x>=3
x=4, 8, 12 or larger
If x=4, e=6
Therefore R=10

But if x=8, e=5 therefore R=13 which is also an option.
Ooops my mistake there, if x = 8 then c - r = 1 then it will be the smallest difference.
Sorry, not my best day lol
0
reply
As.1997
Badges: 16
Rep:
?
#9
Report Thread starter 1 year ago
#9
(Original post by Arctic Kitten)
Ooops my mistake there, if x = 8 then c - r = 1 then it will be the smallest difference.
Sorry, not my best day lol
I’m quite lost. Is my working out wrong?
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#10
Report 1 year ago
#10
(Original post by As.1997)
I’m quite lost. Is my working out wrong?
If x = 8 then
e = 5
r = e + 8 = 13
c = e + 9 = 14
d = e + 11 = 16
so the smallest difference is between c - r = 1, not d - c = 2 as required.
0
reply
As.1997
Badges: 16
Rep:
?
#11
Report Thread starter 1 year ago
#11
(Original post by Arctic Kitten)
If x = 8 then
e = 5
r = e + 8 = 13
c = e + 9 = 14
d = e + 11 = 16
so the smallest difference is between c - r = 1, not d - c = 2 as required.
Thank you 🙏
I'm really quite amazed by how you avoided so many of the "traps".
In case you are interested, I went off track due to several issues which you resolved.

When I first read that the difference between design and construction was 2, I was confused by it because it made it seem like it was possible to have both of these scenarios:
D-C=2 or C-D=2
Similarly, for the largest difference, I had that same issue.
The other problems I had:
1) I didn't realise the biggest difference was the difference between the largest and smallest
2) I didn't realise x had to be greater than or equal to 3
Last edited by As.1997; 1 year ago
0
reply
Arctic Kitten
Badges: 21
Rep:
?
#12
Report 1 year ago
#12
(Original post by As.1997)
Thank you 🙏
BTW when I first read that the difference between design and construction was 2, I was confused by it because it made it seem like it was possible to have both of these scenarios:
D-C=2 or C-D=2
In case you're still confused I answered that earlier.
In a problem like this, if you see ambiguous information, immediately try to find a way to eliminate one of the possibilities. those questions should be solvable in 2 - 3 minutes (or less) ideally, so they won't give you too much, or too little info.
0
reply
As.1997
Badges: 16
Rep:
?
#13
Report Thread starter 1 year ago
#13
(Original post by Arctic Kitten)
In case you're still confused I answered that earlier.
In a problem like this, if you see ambiguous information, immediately try to find a way to eliminate one of the possibilities. those questions should be solvable in 2 - 3 minutes (or less) ideally, so they won't give you too much, or too little info.
Just read it and it makes sense to me now
I really appreciate your help.
1
reply
Arctic Kitten
Badges: 21
Rep:
?
#14
Report 1 year ago
#14
(Original post by As.1997)
Just read it and it makes sense to me now
I really appreciate your help.
No problem! Glad I can help.
1
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
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

Poll: What factors affect your mental health most right now? Post-lockdown edition

Anxiousness about restrictions easing (21)
6.56%
Uncertainty around my education (35)
10.94%
Uncertainty around my future career prospects (37)
11.56%
Lack of purpose or motivation (46)
14.38%
Lack of support system (eg. teachers, counsellors, delays in care) (17)
5.31%
Impact lockdown had on physical health (14)
4.38%
Social worries (incl. loneliness/making friends) (31)
9.69%
Financial worries (22)
6.88%
Concern about myself or my loves ones getting/having been ill (14)
4.38%
Exposure to negative news/social media (19)
5.94%
Difficulty accessing real life entertainment (6)
1.88%
Lack of confidence in making big life decisions (34)
10.63%
Worry about missed opportunities during the pandemic (24)
7.5%

Watched Threads

View All