It is currently Tue Dec 06, 2016 12:50 am

 All times are UTC

 Page 1 of 1 [ 6 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: FPTP style probability questions - how likely ?Posted: Fri Jul 11, 2014 6:03 am

Joined: Sat Dec 28, 2013 3:52 pm
Posts: 845
FPTP Numerical reasoning, book2, Q3

d. What is the probability of picking one black ball and one white ball on the first two rounds, before both are replaced ?

Total no of balls = 12, Black balls = 6, white balls = 4, spotted balls = 2.

Answer: Probability of picking a black ball = 6/12, Probability of picking a white ball = 4/11, two rounds hence - 6/12*5/11*2

DD says, what if i pick a white ball before black ball or what if I pick two balls at one time ? They haven't given a sequence i.e pick black ball before white.
At the moment her understanding of 'and' is picking simultaneously. Is there any default rule ?

Finally, how likely are these type of questions for CEM exam ?

Last edited by berks_mum on Fri Jul 11, 2014 3:26 pm, edited 1 time in total.

Top

 Post subject: Re: FPTP style probability questions - how likely ?Posted: Fri Jul 11, 2014 7:48 am

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11940
6 + 4 + 4 is not 12

This should not be on an 11+ paper in my opinion ...

Top

 Post subject: Re: FPTP style probability questions - how likely ?Posted: Fri Jul 11, 2014 3:25 pm

Joined: Sat Dec 28, 2013 3:52 pm
Posts: 845
sorry, typo, it should be spotted = 2.

Top

 Post subject: Re: FPTP style probability questions - how likely ?Posted: Fri Jul 11, 2014 3:40 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11940
Quote:
d. What is the probability of picking one black ball and one white ball on the first two rounds, before both are replaced ?

Total no of balls = 12, Black balls = 6, white balls = 4, spotted balls = 2.

Black then white = 6/12 x 4/11

white then black = 4/12 x 6/11

Both probabilities are the same (ie order doesn't matter) so total prob is doubled (two added together) because of the two ways.

This is more like a GCSE question imho.

Top

 Post subject: Re: FPTP style probability questions - how likely ?Posted: Mon Jul 14, 2014 9:41 am

Joined: Sat Dec 28, 2013 3:52 pm
Posts: 845
Same book, FPTP Numerical reasoning, Book2, Test 5,

Q3. Theo rolls two fair dice consecutively and records the results.

c) What is the probability that the sum of the numbers displayed on the two dice is 10 ?

Answer: 36 different combinations of numbers can be achieved by rolling the two dice as 6x6 = 36. The two dice will add up to 10 in three combinations : 5/5, 4/6 and 6/4. The probability of the sum of the two dice being 10 is 3/36 (simplified to 1/12).

d) What is the probability of part c occurring twice in a row ?

=================================================================================================================================

Again, is combinations a part of ks2 syllabus ? Should the DCs be prepared for such questions or best ignored ?
Needless to say DD wasn't able to do this question and the next one(d) as it was based on this.

Top

 Post subject: Re: FPTP style probability questions - how likely ?Posted: Mon Jul 14, 2014 9:43 am

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11940
Not part of KS2 syllabus at all ..

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 6 posts ]

 All times are UTC

#### Who is online

Users browsing this forum: No registered users and 4 guests

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ FORUM RULES    Forum Rules and FAQs 11 PLUS SUBJECTS    VERBAL REASONING    MATHS    ENGLISH    NON-VERBAL REASONING    CEM 11 Plus GENERAL    GENERAL 11 PLUS TOPICS    11 PLUS APPEALS    11 PLUS TUTORS    INDEPENDENT SCHOOLS    11 PLUS CDs/SOFTWARE    11 PLUS TIPS    PRIMARY    SEN and the 11 PLUS    EVERYTHING ELSE .... 11 PLUS REGIONS    Berkshire    Bexley and Bromley    Birmingham, Walsall, Wolverhampton and Wrekin    Buckinghamshire    Devon    Dorset    Essex    Essex - Redbridge    Gloucestershire    Hertfordshire (South West)    Hertfordshire (Other and North London)    Kent    Lancashire & Cumbria    Lincolnshire    Medway    Northern Ireland    Surrey (Sutton, Kingston and Wandsworth)    Trafford    Warwickshire    Wiltshire    Wirral    Yorkshire BEYOND 11 PLUS    Beyond 11 Plus - General    GCSEs    6th Form    University
Privacy Policy | Refund Policy | Disclaimer | Copyright © 2004 – 2016