Hey! Sign in to get help with your study questionsNew here? Join for free to post

Stats (S1) H/W *urgent help needed please*

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
    • Thread Starter

    Hi there,I need some help with my stats homework. I am really struggyling with stats and need some advice on how to improve.There are 15 students, 15 chairs, 4 wear glasses, 7 wear hoodies.How many ways can you sit on these chairs: 1. so that Richard and David do not move2. so that Robert and Hannah stay sitting next to each other3. so that the students wearing glasses sit next to each other 4. so that Joe and Megan are sitting 'at the ends'5. so that the students wearing hoodies do not sit next to each other and those without do not sit next to each other 6. so that James does not sit next to Ben.*Apparently the hardest question. so that the students wearing glasses do not sit next to each other.

    I'm not an expert on S1 but this how I think it works...

    1. For this part, you know that Richard and David must sit where they currently are sitting. This means then that those two seats are taken so there are only 13 seats left. Since the order in which they are sitting matters it is a permutation, meaning that the total arrangements of people on the remaining seats is 13 Factorial (!).

    2. Robert and Hannah stay sitting next two each other, can be thought of as their two chairs being joined together, this means that there are now effectivley 14 chairs, so there would be 14! ways of sitting on those chairs. However, Robert and Hannah can sit on the 'joined chair' in two possible ways (Robert, Hannah or Hannah, Robert). This means then that the 14! arrangement must be multiplied by a further 2 arrangements.

    3. If you look at this question the same ways as question 2, you should get the right answer, just remember that there are now 4 chairs joined so an additional 4! arrangements to multiply at the end.

    4. Let Joe and Megan sit at the end then you are left with 13 seats, work out the number of ways those remaining 13 seats are filled and multiply by the number of ways Joe and Megan can sit at the ends.

    I'm not too sure about 5.

    6. Find the total number of arrangements of all the seats, then subtract the ways in which James and Ben DO sit together. This will leaves the number of ways they don't.

    In my opinion this is the hardest part about S1, and I think the only thing that makes it easier is to just practise loads of these types of questions. Also, drawring diagrams and thinking logically about each question helps.
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: October 13, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Do you like sleeping in a cold room?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read here first


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
Study resources

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

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