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# Edexcel S2 - 27th June 2016 AM watch

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1. (Original post by Kitkat5)
5. Four coins are flipped together and the random variable H represents the number of headsobtained. Assuming that the coins are fair,
Given that the four coins are all biased such that the chance of each one showing a head is50% more than the chance of it showing a tail,
(d) find the probability of obtaining more heads than tails when the four coins are flippedtogether.

how would you guys do this? i'm so confuuzzled
The probabilities are in a ratio of 1.5:1, or 3:2. Therefore 1/5 = 0.2 and probability of a head is 3 * 0.2 = 3/5.
2. (Original post by Kitkat5)
Exactly, Idk? I thought it would be 3/4 but the mark scheme says 3/5
It says 50% MORE

Meaning that the probability of a head = 1.5* probability of a tail

(2/5)*1.5 = 3/5
3. Good luck fellas.
4. (Original post by Mattematics)
The probabilities are in a ratio of 1.5:1, or 3:2. Therefore 1/5 = 0.2 and probability of a head is 3 * 0.2 = 3/5.
yeah but why (((((((((((((((((((((((((((((((( (((((((((
I saw that in the mark scheme but i don't understand that ratio stuff
5. Can somebody explain how to do part D?

6. Is this exam in the morning

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7. (Original post by Kitkat5)
yeah but why (((((((((((((((((((((((((((((((( (((((((((
I saw that in the mark scheme but i don't understand that ratio stuff
To be fair, I would recommend watching some GCSE videos.

Imagine if you have john, dave and mick, with a bag of rice.
Splitting 6 rice portions in equal parts.

2 goes to john, 2 goes to dave and 2 goes to mick

Then John gets 2 out of the 6, so his proportion of the total rice portions is 2/6, and so on for dave and mick
8. (Original post by RetroSpectro)
It says 50% MORE

Meaning that the probability of a head = 1.5* probability of a tail

(2/5)*1.5 = 3/5
Since I don't understand it i might just cram it.

So if it was 75% more likely woudl the ratio be 1.75:1 ? and 50% less likely would it be... 0.50:1??/
9. (Original post by Supermanxxxxxx)
Is this exam in the morning

Posted from TSR Mobile
Yeah.

Good luck everyone! Hopefully the questions are worded in a nice way :P
10. (Original post by sana_97)
How many past papers should have you done before the exam?
Depends how intelligent you are/What UMS you need to get.

Generally you should have done from jan 2010 all the way to jun 2015 including all the januaries inbetween
11. (Original post by Kitkat5)
Since I don't understand it i might just cram it.

So if it was 75% more likely woudl the ratio be 1.75:1 ? and 50% less likely would it be... 0.50:1??/
Yes exactly
12. (Original post by LukeB98)
Yeah.

Good luck everyone! Hopefully the questions are worded in a nice way :P
Time to do an all nightier then

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13. (Original post by Armpits)
To be fair, I would recommend watching some GCSE videos.

Imagine if you have john, dave and mick, with a bag of rice.
Splitting 6 rice portions in equal parts.

2 goes to john, 2 goes to dave and 2 goes to mick

I.e. 2 : 2 : 2

Then John gets 2 out of the 6, so 2/6, and so on for dave and mick
I know what ratios mean/ i just don't understand how they got that ratio from the question.
I would have thought of it as 150% of the original probability so 3/4 but nvm
14. (Original post by apzoe)
Can somebody explain how to do part D?

Skim read it, but it seems like it's just the probability that the time she has to wait before being served is greater than or equal to 8.
15. (Original post by Jangolite123)
Depends how intelligent you are/What UMS you need to get.

Generally you should have done from jan 2010 all the way to jun 2015 including all the januaries inbetween
Alright Thanks
16. (Original post by Armpits)
Skim read it, but it seems like it's just the probability that the time she has to wait before being served is greater than or equal to 8.
She's already been queing for 5 minutes and the max additional time she can queue for is another 3 minutes. 5+3=8
17. (Original post by Funnycatvideos)
She's already been queing for 5 minutes and the max additional time she can queue for is another 3 minutes. 5+3=8
No ****. Thanks for the basic arithmetic. Said I skim read it, so didn't check the context really.
18. (Original post by RetroSpectro)
Yes exactly
How do I do question 1b and c

https://57a324a1a586c5508d2813730734...%20Edexcel.pdf
19. It's just that there have been several exercises already in past papers with questions like "given that.. find that..".

I know you have to apply the formula P(B|A)=P(A intersection B)/P(A). It's just about using it correctly, right?
20. These questions are so ******** Why are the grade boundaries so high for this

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