Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter
    Offline

    3
    ReputationRep:
    You have eight numbered balls ~ 1,2,3,4,5,6,7,8

    You choose three numbered balls which appeal to you. Say 1,2,3.

    Then you put the eight numbered balls in a bag and pick out three balls.

    What is the probability of you then pulling out 1,2 and 3?
    Offline

    11
    ReputationRep:
    (Original post by Fonda1971)
    You have eight numbered balls ~ 1,2,3,4,5,6,7,8

    You choose three numbered balls which appeal to you. Say 1,2,3.

    Then you put the eight numbered balls in a bag and pick out three balls.

    What is the probability of you then pulling out 1,2 and 3?
    Do you mean 1, 2, 3 in that order or 1, 2, 3, in any order? Please post what you've tried so far and say exactly where you're stuck.
    • Thread Starter
    Offline

    3
    ReputationRep:
    Hi, thanks for helping.

    1,2,3 in any order.

    I’ve no clue how to work this question out and would appreciate any help!
    Offline

    17
    ReputationRep:
    Q1) How many ways are there of choosing 3 balls from 1, 2, 3, ..., 8?
    Q2) How many ways are there of choosing 1, 2, 3 from 1, 2, 3, ... 8?

    Note: "choosing" has a technical meaning here - it means "order doesn't matter, just which balls you end up with". So {1, 2, 3} would be the same as {2, 1, 3} etc.

    The probability you require is the answer to Q2 divided by the answer to Q1.
    • Thread Starter
    Offline

    3
    ReputationRep:
    [
    I do apologise, it’s a completely hypothetical question but an answer would help a real life situation. In my sons math class, 3 boys out of eight boys were chosen by their teacher to be given an opportunity to be taken to a museum. A parent complained that this was unfair - that this opportunity should have been open to everyone and not just the teachers ‘favorite’ kids. this was put to the teacher who then said he would put the names of the eight boys in class into a hat and pull three names out randomly. Incredibly, the outcome was the same ~ the names of the three boys he had originally chosen were pulled out of the hat. Of course, this was done in private. My son cried ‘fix’ so, I’d like to show him the probability of this occurring in real life.
    Offline

    17
    ReputationRep:
    (Original post by Fonda1971)
    [
    I do apologise, it’s a completely hypothetical question but an answer would help a real life situation. In my sons math class, 3 boys out of eight boys were chosen by their teacher to be given an opportunity to be taken to a museum. A parent complained that this was unfair - that this opportunity should have been open to everyone and not just the teachers ‘favorite’ kids. this was put to the teacher who then said he would put the names of the eight boys in class into a hat and pull three names out randomly. Incredibly, the outcome was the same ~ the names of the three boys he had originally chosen were pulled out of the hat. Of course, this was done in private. My son cried ‘fix’ so, I’d like to show him the probability of this occurring in real life.
    Maths forum rules are we help people to solve questions rather than tell them the answer, but I'll make an exception here...

    probaility is 1 in (8 * 7 * 6 / 6) or 1 in 56 (about 1.8%).
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Fonda1971)
    [
    I do apologise, it’s a completely hypothetical question but an answer would help a real life situation. In my sons math class, 3 boys out of eight boys were chosen by their teacher to be given an opportunity to be taken to a museum. A parent complained that this was unfair - that this opportunity should have been open to everyone and not just the teachers ‘favorite’ kids. this was put to the teacher who then said he would put the names of the eight boys in class into a hat and pull three names out randomly. Incredibly, the outcome was the same ~ the names of the three boys he had originally chosen were pulled out of the hat. Of course, this was done in private. My son cried ‘fix’ so, I’d like to show him the probability of this occurring in real life.
    Out of interest, what are you going to tell your son?

    1.8% is a low probability but not impossible and unlikely events happen all the time
    • Thread Starter
    Offline

    3
    ReputationRep:
    Thank you so much for the answer and for making an exception. That’s great and I can now explain this in easy terms to my son. Kindest Regards.
    • Thread Starter
    Offline

    3
    ReputationRep:
    And at least my son is vindicated having thought it was perhaps a fix! With a chance of 1.8% I think his hunch was right.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 19, 2017
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.