Turn on thread page Beta
    • Thread Starter
    Offline

    9
    ReputationRep:
    14) A prime number between 300 and 450 is chosen at random. The table shows the probability that the number lies in different ranges.

    Prime number, n Probability
    300 ⩽ n < 330 0.16
    330 ⩽ n < 360 0.24
    360 ⩽ n < 390 x
    390 ⩽ n < 420 0.16
    420 ⩽ n < 450 0.24

    14 (a) Work out the value of x.
    [2 marks]



    14 (b) Work out the probability that the prime number is greater than 390
    [1 mark]


    14 (c) There are four prime numbers between 300 and 330
    How many prime numbers are there between 300 and 450?
    [2 marks]

    I don't understand the mark scheme do you guys have another method to work this out?
    Offline

    21
    ReputationRep:
    (Original post by GCSE_18)
    14) A prime number between 300 and 450 is chosen at random. The table shows the probability that the number lies in different ranges.

    Prime number, n Probability
    300 ⩽ n < 330 0.16
    330 ⩽ n < 360 0.24
    360 ⩽ n < 390 x
    390 ⩽ n < 420 0.16
    420 ⩽ n < 450 0.24

    14 (a) Work out the value of x.
    [2 marks]



    14 (b) Work out the probability that the prime number is greater than 390
    [1 mark]


    14 (c) There are four prime numbers between 300 and 330
    How many prime numbers are there between 300 and 450?
    [2 marks]

    I don't understand the mark scheme do you guys have another method to work this out?
    Remember that the sum of probabilities =1 and that will solve the first part.

    The second part is adding together the probabilities of finding prime numbers in certain regions that contain prime numbers greater than 390.

    The third part is using that the prime numbers are chosen at random so that each prime number has probability 1/N, where N is the number of prime numbers between 300 and 450.
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by Dalek1099)
    Remember that the sum of probabilities =1 and that will solve the first part.

    The second part is adding together the probabilities of finding prime numbers in certain regions that contain prime numbers greater than 390.

    The third part is using that the prime numbers are chosen at random so that each prime number has probability 1/N, where N is the number of prime numbers between 300 and 450.
    Thank you but I'm still lost on the third one?
    Offline

    21
    ReputationRep:
    (Original post by GCSE_18)
    Thank you but I'm still lost on the third one?
    Each prime number has probability 1/N and you are given the number of prime numbers between 300 and 330 and thus you can work out an expression for the probability of finding a prime number between 300 and 330 and then you equate this with the probability of finding a prime number between 300 and 330 given in the table and then solve for N.
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by Dalek1099)
    Each prime number has probability 1/N and you are given the number of prime numbers between 300 and 330 and thus you can work out an expression for the probability of finding a prime number between 300 and 330 and then you equate this with the probability of finding a prime number between 300 and 330 given in the table and then solve for N.
    Oh, thank you very much.
    • TSR Support Team
    Online

    21
    ReputationRep:
    TSR Support Team
    (Original post by GCSE_18)
    14) A prime number between 300 and 450 is chosen at random. The table shows the probability that the number lies in different ranges.

    Prime number, n Probability
    300 ⩽ n < 330 0.16
    330 ⩽ n < 360 0.24
    360 ⩽ n < 390 x
    390 ⩽ n < 420 0.16
    420 ⩽ n < 450 0.24

    14 (a) Work out the value of x.
    [2 marks]



    14 (b) Work out the probability that the prime number is greater than 390
    [1 mark]


    14 (c) There are four prime numbers between 300 and 330
    How many prime numbers are there between 300 and 450?
    [2 marks]

    I don't understand the mark scheme do you guys have another method to work this out?
    Hi there :wavey:
    I've moved your thread to the Maths forum where hopefully you'll get more answers In future, it's best to select the subject from the list here and create a thread in there instead :yep: If you want to see where threads belong, check out this thread
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by Lemur14)
    Hi there :wavey:
    I've moved your thread to the Maths forum where hopefully you'll get more answers In future, it's best to select the subject from the list here and create a thread in there instead :yep: If you want to see where threads belong, check out this thread
    Oh, I never knew I should probably start doing that, thank you.
    • TSR Support Team
    Online

    21
    ReputationRep:
    TSR Support Team
    (Original post by GCSE_18)
    Oh, I never knew I should probably start doing that, thank you.
    You're welcome

    Posted from TSR Mobile
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 4, 2018
Poll
Do you think parents should charge rent?
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.