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# S1- Edexcel Really quick probability question Tweet

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1. S1- Edexcel Really quick probability question
Hi, exam tommorow and panicking because i don't get this!

Q: The spinner is spun repatedly and S counters are awarded on the outcome of each spin. If S is even then Tom recieves the counters and if S is off then Jess recieves them. The 1st player to collect 10 or more counters is the winner

So the probabilities
P(0)=0.1
P(1)=0.25
P(2)=0.25
P(4)=0.2
P(5)=0.2

So the part of the question i'm stuck on:
(f) Find the probability Jess wins after eactly 3 spins

So i did the arrangments (5,0,5)
(5,5,0) and (0,5,5) and went from there but got it wrong?!

2. Re: S1- Edexcel Really quick probability question
(5,0,5),(0,5,5),(5,1,5),(1,5,5), (5,2,5),(2,5,5),(5,4,5),(4,5,5)

= 2(0.2*0.1*0.2)+4(0.2*0.2*0.25)+2 (0.2*0.2*0.2) = 0.064

This is because if he wins 5 on the first go and then loses on the second (if its even), as long as he gets 5 on the last go he will have 10 spinners and win
+ It can't be (5,5,0) because he would have 10 counters before the third spin.

Another simpler way to do it:
This is what is happening:
Him winning 5 in the first spin, not winning in the second one and then winning in the third OR not winning in the first, then winning in the second and third spin.

So the probably of not having 5 is 0.8 and probably of having 5 is 0.2

(0.2*0.8*0.2)+(0.8*0.2*0.2) so basics 2(0.2*0.2*0.8) = 0.064
3. Re: S1- Edexcel Really quick probability question
Hi! How did you find the exam??
4. Re: S1- Edexcel Really quick probability question
5. Re: S1- Edexcel Really quick probability question
(Original post by ummi1)
Hi! How did you find the exam??

(Original post by Keethan)
Horrible man, I didn understand the histogram problem. I was not able to find the area
Guys don't discuss the exam until the correct amount of time has elapsed. Mods will get ya into trouble. Here is more info on this:

http://www.thestudentroom.co.uk/anno...php?f=38&a=629
6. Re: S1- Edexcel Really quick probability question
Will they be giving some marks for the hsitogram sum? THEY DIDN MENTION THE VALUES FOR FREQUENCY DENSITY
7. Re: S1- Edexcel Really quick probability question
I'm not too sure ... I hope they made a mistake publishing it :/ because that was the only question the wasn't straight forward

How did you find the last question on probabilities?
8. Re: S1- Edexcel Really quick probability question
Well that was kinda okay, not too difficult. I am just scared for the frequency density sum.. I didnt know what to do, whether to assume the value it or just leave it. i wasted a lot of time, didn have time to check my other answers..Did you do that sum?
9. Re: S1- Edexcel Really quick probability question
(Original post by A*'s)
I'm not too sure ... I hope they made a mistake publishing it :/ because that was the only question the wasn't straight forward

How did you find the last question on probabilities?
they told you total people so you could work out fd
10. Re: S1- Edexcel Really quick probability question
(Original post by TenOfThem)
they told you total people so you could work out fd
I did it this way:
I used a cm scale to measure width and height of the bars.
So this gives,
1*1.5 + 2*6 + 1*4.5 + 1*1.5 + 1*3 = 22.5cm^2
22.5cm^2 = 450cars
1cm^2 = 20cars

Area of bars (35-40) and (40-45),
1*1.5 + 1*3 = 4.5cm^2
4.5cm^2 = 90 cars

Another question, you may be able to answer it, i got stuck in the probability question(last question of the paper), i had about 20-25 minutes left for that so i tried everything at it.
The first part of it was easy.
For the second part i did 2 attempts and for the third i did 4 attempts, in both parts i did get answers of Arsey in one of those attempts.
In that last part i got the correct answer.
Will i get full marks in this question? I think alternative solutions are allowed.
11. Re: S1- Edexcel Really quick probability question
(Original post by raheem94)
Will i get full marks in this question? I think alternative solutions are allowed.

Morning

If you gave more than one answer you get 0 marks

If you gave the correct answers then your method must have been suitable so full marks
12. Re: S1- Edexcel Really quick probability question
(Original post by TenOfThem)
Morning

If you gave more than one answer you get 0 marks

If you gave the correct answers then your method must have been suitable so full marks

Aren't alternate solutions allowed in A-Level edexcel maths?
13. Re: S1- Edexcel Really quick probability question
(Original post by raheem94)

Aren't alternate solutions allowed in A-Level edexcel maths?
That is what I said ... if your answer was correct then your method must have been suitable so full marks
14. Re: S1- Edexcel Really quick probability question
(Original post by TenOfThem)
That is what I said ... if your answer was correct then your method must have been suitable so full marks
Do they accept any method as long as you get the right answer?

e.g. in FP2 with differential equations, sometimes you can end up taking ages using product/quotient rules for implicit differentiation, but it can be quicker to use partial derivatives (but not always). If you wrote "I have done this part of the question using the rule _____", would it be okay?
15. Re: S1- Edexcel Really quick probability question
(Original post by TenOfThem)
That is what I said ... if your answer was correct then your method must have been suitable so full marks
My problem is something different.

I got 2 answers for part 'b' of the last question and 4 answers for part 'c' of the last question. In both of those parts i did got one answer which matched with Arsey.

So actually out of 2 attempts for part 'b', my one attempt was correct, and out of 4 attempts for part 'c', my one attempt was correct.

Will i get full marks if the attempt which gave the correct answer was suitable?
16. Re: S1- Edexcel Really quick probability question
(Original post by raheem94)
My problem is something different.

I got 2 answers for part 'b' of the last question and 4 answers for part 'c' of the last question. In both of those parts i did got one answer which matched with Arsey.

So actually out of 2 attempts for part 'b', my one attempt was correct, and out of 4 attempts for part 'c', my one attempt was correct.

Will i get full marks if the attempt which gave the correct answer was suitable?
Not if you left all of the answers

It is my understanding that "choice of answers = 0 marks" ... it is a couple of years since I marked for Edexcel so this may have changed ... but I doubt it
17. Re: S1- Edexcel Really quick probability question
(Original post by Zhy)
Do they accept any method as long as you get the right answer?

e.g. in FP2 with differential equations, sometimes you can end up taking ages using product/quotient rules for implicit differentiation, but it can be quicker to use partial derivatives (but not always). If you wrote "I have done this part of the question using the rule _____", would it be okay?
Depends

Not always

But usually they will unless it (a) states a method or (b) says a method will gain no marks
18. Re: S1- Edexcel Really quick probability question
(Original post by TenOfThem)
Not if you left all of the answers

It is my understanding that "choice of answers = 0 marks" ... it is a couple of years since I marked for Edexcel so this may have changed ... but I doubt it
Arsey just replied to me. See this post.

I once asked this question to an edexcel examiner on TSR, her reply was:
If you give several versions of an answer and don't cross any of them out, the examiner will read all of them and give you the marks for the best version.
19. Re: S1- Edexcel Really quick probability question
(Original post by raheem94)
Arsey just replied to me. See this post.

I once asked this question to an edexcel examiner on TSR, her reply was:
If you give several versions of an answer and don't cross any of them out, the examiner will read all of them and give you the marks for the best version.
As I say it is a few years since I stopped marking for Edexcel so there must have been a policy change
20. Re: S1- Edexcel Really quick probability question
(Original post by raheem94)
Arsey just replied to me. See this post.

I once asked this question to an edexcel examiner on TSR, her reply was:
If you give several versions of an answer and don't cross any of them out, the examiner will read all of them and give you the marks for the best version.
I don't understand... how can that possibly be allowed? What's to stop someone from just writing every possible permutation that the answer could be?