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 Posted: Sat May 10, 2014 3:26 pm

Joined: Wed May 18, 2011 10:56 am
Posts: 217
Hi,
Can anyone explain the answer to test1 3d, I understand the first part, answer is 2/11,
the final anwer is 4/11. They multiply by 2 to get the 4/11..?? I find the answer quite confusing, have read it numerous times.

I'm normally ok with probability but this is a challenge. Its taken me time to understand this question. Need to clarify the 4/11. Please can someone explain the above.

Thanks

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 Posted: Mon May 12, 2014 8:33 am

Joined: Mon Aug 12, 2013 9:13 am
Posts: 452
Can you please post the question (unless it has some images)?

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 Posted: Wed May 14, 2014 11:30 pm

Joined: Wed Mar 20, 2013 1:16 pm
Posts: 76
Probability of picking a black ball out of 6 black and 12 total number of balls is 6/12 = 1/2
Prob of picking a white ball without replacing the black ball = 4/11 (4 white balls out of 11)
Total probability of picking a black and then white ball is 1/2X4/11 = 4/22 = 2/11

There are 2 rounds of this game so proability = 2 X 2/11 = 4/11

Hope that helps

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 Posted: Thu May 15, 2014 8:16 am

Joined: Mon Aug 12, 2013 9:13 am
Posts: 452
Haven't seen the question but can guess what it is. OMG - that's way hard for any year 6 or 7 child........forget 10 year being able to solve. I don't think it is any relevant to CEM by large distance. BTW which publisher is it from?

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 Posted: Tue May 20, 2014 7:51 am

Joined: Wed May 18, 2011 10:56 am
Posts: 217
Hi,
Sorry been busy didn't get chance to see reply.... this q is from Book 2 FPTP, I had to look at the answer to understand..dd understtod before me

Thanks for the reply Gulat ...is clear. I also hope they dont get confusing q's like this.

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 Posted: Tue May 20, 2014 12:14 pm

Joined: Mon May 19, 2008 9:39 pm
Posts: 522
hasmum wrote:
Hi,
Sorry been busy didn't get chance to see reply.... this q is from Book 2 FPTP, I had to look at the answer to understand..dd understtod before me

Thanks for the reply Gulat ...is clear. I also hope they dont get confusing q's like this.

I have been told that FPTP books are often far harder than we should expect - and more time pressured. Is this others understanding too?

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 Posted: Tue May 20, 2014 3:53 pm

Joined: Mon Aug 12, 2013 9:13 am
Posts: 452
I can't comment on FPP (mods are listening )

I think there has to be a right balance between morale booster and confidence breaker. Some hard stuff with poor score at the end stages might have a negative impact. I prefer material that reflects the real exam and are not too easy or too hard.

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