2011
Fri
11
Nov

# GCE A Level 2011 Oct/Nov H2 Maths 9740 Paper 2 & H1 Maths 8864 Paper 1 Suggested Answers & Solutions

(36)
Posted at 10:32 pm

Hello it’s me again *rubs eyes*

It’s been a looooooong day. And yeah the A Level Maths papers have been a little tricky this year.

While I recognize that many of have had a tough time working out the papers for the past two mornings, do spare a thought for me who have been forced by my sis to working out three A Level Maths papers in the past two days (plus tuition time) as you browse through my suggested answers to today’s H2 Maths Paper 2 which you may access here by clicking the button (if you haven’t yet done so).

H2 Maths Paper 2

• 1.1:
Q2(ii) Modified rejection reason to 2x < n (as kindly pointed out by Chen Jing)
Q3(iii): x = -0.4847 instead of -0.4877 (misread due to pen no ink )
Q8(iv): 13.5 – corrected rounding error (as kindly pointed out by Ah Wei)
Q12(iii) – removed lower limit of 0 since there’s nothing stopping the number of people joining the queue to be greater than the number leaving the queue (as pointed out by sam)
• 1.2:
Q2(ii) – Simplified the final answer further.
Q8(i) – Removed extra point from scatter diagram which should contain only 5 points (I swear I plotted only 5 points that night!!!)
Q12(iii) – removed the continuity correction since the approximated aggregated Normal distribution is already continuous. Therefore no continuity correction is needed (apologies for this oversight and I hope this will bring closure to this part).
Q12(iv) – added missing answer (too tired that night and missed this!)
GCE A Level H2 Maths 9740 Paper 2 (left) H1 Maths 8864 Paper 1 (right)

As usual, please leave a comment should you spot any mistake in this set of suggested solutions – as mentioned it’s been rather tiring doing the many, many A Level Maths papers these two days *faints*

Last but not least, if you haven’t yet done so, do say hi to me when you drop by in Facebook

### Revision Exercise

To show that you have understood what Miss Loi just taught you, you must:

1. sam says

2011
Nov
11
Fri
10:42pm

1

12 part three. why is there a bottom limit of zero. shouldnt it be just P(Y-X <11.5) ?

• Trex replied to sam’s comment

2011
Nov
11
Fri
11:01pm

1.1

@sam: Coz you're supposed to "assume that the queue does not become empty during this period".

• Trex replied to Trex’s comment

2011
Nov
11
Fri
11:04pm

@Trex: Nono, i think i interpreted wrongly Sorry.
PS: remove my comment T_T

• 2011
Nov
16
Wed
7:16pm

1.2

@sam: Yes there shouldn't be a lower limit of 0 since there is a possibility that the number of people joining the queue is greater than the number leaving the queue.

This has been amended in v1.1.

2. Ah Wei says

2011
Nov
11
Fri
10:48pm

2

For 8iv) must note to use 5sf and above to find value of y. If not will have rounding off errors.

• 2011
Nov
16
Wed
7:34pm

2.1

@Ah Wei: Amended in version 1.1. Thanks for pointing this out!

3. Anonymous says

2011
Nov
11
Fri
10:53pm

3

Question 2 part (ii) : it should be x < 2n ,and not x < n. n/12(6 + root(12)) is still smaller than n

• 2011
Nov
16
Wed
7:36pm

3.1

Amended in v1.1 as described here

4. Chen jing says

2011
Nov
11
Fri
11:02pm

4

Hi! I think the rejection reason for the rectangle should be 2x<n if u looked at the left side! Cause one of the x value is ard 0.2n the other 0.7n so
Reject the 0.7n

• 2011
Nov
16
Wed
7:35pm

4.1

Thanks for pointing this out. Amended in v1.1 - sorry a bit cuckoo-eyed that night

5. fran says

2011
Nov
11
Fri
11:06pm

5

h2 math paper2, question 12 part iii) shouldnt it be X + Y instead of X-Y ??

6. yellowfishx says

2011
Nov
11
Fri
11:16pm

6

Hi,
For 12iii, there should not be a lower limit of 0, as the number of people entering the queue can be more than number of people leaving.
In addition, continuity correction should not be used, as the distribution of Y15-X15~N(9,45) is not based on a poisson distribution.
seems like it's more tricky than you thought

• 2011
Nov
16
Wed
7:31pm

6.1

Sorry I've been away in the past days.

Yes a continuity correction is used only when the distribution modeled is discrete. In this case, the aggregated normal distribution is already continuous (though it is approximated) so a further continuity correction is unnecessary.

Therefore no continuity correction is needed and I've amended the solutions to reflect this in v1.2.

Apologies for this oversight and I hope this will bring closure to everyone on this part.

P.S. The lower limit issue has be corrected since v1.1.

7. james says

2011
Nov
11
Fri
11:24pm

7

omgg... got average of 70 for both papers only... that isnt an A right

• xiuxiu replied to james’s comment

2011
Nov
12
Sat
10:54am

7.1

@james: same! damn sian I screw up paper 1. wondering wat's the cut off for A this yr!

8. sw says

2011
Nov
11
Fri
11:26pm

8

continuity correction should be to P(R<25.5) rather than P(R<24.5)?

• 2011
Nov
16
Wed
10:10pm

8.1

@sw: Refer to this comment last year for some heads up on continuity correction.

In short, for the CC in Q7(iv), P(R < 25) becomes P(R < 24.5) ∵ 25 is not included in the interval.

9. john says

2011
Nov
11
Fri
11:28pm

9

But mdm, isnt there is chance that the queue will get longer instead?

10. Curious says

2011
Nov
11
Fri
11:48pm

10

Hi, for 12iii, considering that there's a subtraction between both approximated distributions, isn't cc not needed? Thanks for the answers!

• 2011
Nov
16
Wed
7:47pm

10.1

@Curious: I've removed the continuity correction (cc) step for Q12(iii) in version 1.2.

However, the reason has more to do with the fact that the final approximated normal distribution is continuous (and not a discrete Poisson distribution anymore) that leads to cc being unnecessary.

CC would be required if the final modeled distribution is discrete, regardless of whether it is the result of any 'subtraction' or 'addition' between distributions.

11. 2011
Nov
12
Sat
11:48am

11

SOrry just Wondering whether the scatter diagram is y on
X or y on x^2?

• 2011
Nov
16
Wed
8:22pm

11.1

The scatter diagram is y on x so that you can show clearly the non-linear relationship between y and x in your scatter diagram.

Please note that you should simply sketch using arbitrary points as required by the instructions in Q9(i) i.e.
a is positive ⇒ positive y-intercept
b is negative ⇒ plots negatively sloped
equally-spaced positive x- and y-values ⇒ all points in first quadrant

You should not waste time plotting using the data in the table (or worse use all 7 points in your scatter diagram when you are instructed to include only 5) which is actually meant for subsequent parts.

12. clarionx says

2011
Nov
12
Sat
12:28pm

12

oh and 7i) can i say that 1 of the assumptions is to assume that the calls are independent of one another?

• 2011
Nov
16
Wed
8:26pm

12.1

@clarionx: Yes, a binomial model requires the calls to be independent of each other i.e. who I call now will have no bearing on who I call next and vice versa.

13. 2011
Nov
12
Sat
7:37pm

13

In my opinion it is one of the more difficult year so the A should be about 70-73 prolly:) don't worry if u get 70 and above

14. Mac says

2011
Nov
13
Sun
9:25am

14

For 12iii) can't you do E( 35+X-Y) where 35+X-Y is the people left in the queue? And Qn11i) is it possible to do R~B(10,0.6) then find P(R=4)?

• 2011
Nov
16
Wed
9:15pm

14.1

@Mac: For Q12(iii), P("at most 11 people left the queue overall by 0945") as described in the suggested solution vs P("at least 24 people in the queue by 0945") yields the same outcome.

I suppose your workings is as follows, in which case is fine:

X ~ Po(27) → X ~ N(27, 27) approximately
Y ~ Po(18) → X ~ N(18, 18) approximately

No. of people in queue at 0945,
W ~ N(35 + 18 − 27, 18+27)
W ~ N(26, 45)
P(W ≥ 24) ≈ 0.617 (3sf)

As for Q11(i), this is actually a question on Permutations & Combinations where P(R = 4) is the probability of getting a combination of 4 women in the committee of 10 (18C4 × 12C6), out of every possible combination of choosing a committee of 10 from 30 people (30C10).

If you do B(10, 0.6), P(R = 4) would then refer to the probability of picking a woman 4 times out of 10 independent tries. This scenario is different from the first and will give you a different answer which will result in you having difficulty in proving part (ii).

15. karl says

2011
Nov
15
Tue
7:03pm

15

my math teacher once told me that there is no bell curve for math. because too many people do well..he and i may be wrong. oh well, this is def more difficult than last year's. I'm between 70-75 hope i get an A. I NEED THE A...like i have the right to dismiss everyone else because i got a conditional offer from UK. HAHA, everybody, good luck!

16. weng says

2012
May
29
Tue
2:09am

16

hmm, are the question paper be uploaded too

17. weng says

2012
May
29
Tue
2:09am

17

can the question pape r be uploaded

• 2012
Jun
12
Tue
10:39pm

17.1

@weng: This diagram illustrates what will probably happen should Miss Loi commit SEAB treason by uploading the hallowed question papers

18. Jess says

2012
Nov
7
Wed
1:41pm

18

Hi, when will the H2 maths 2012 A Level answers be out?

Thanks!

• 2012
Nov
7
Wed
9:20pm
19. Joey says

2012
Nov
7
Wed
2:07pm

19

Hi, will you guys upload the answers for this year's H1/H2 math papers? Thanks so much!

• 2012
Nov
7
Wed
9:21pm
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