11 Plus Exams Forum

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

Can you please post the question (unless it has some images)?

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

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?

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.

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?

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.