Hey there! Sign in to join this conversationNew here? Join for free
    • Study Helper
    • Thread Starter
    Offline

    20
    ReputationRep:
    Study Helper
    Hi!
    This kind of problem confuses me. For this particular one, I have the mark scheme but I don't understand why you have to do each step.

    Could someone go through how you would do this question, why you do each step? + Help me outline a way of tackling them.

    Thank you!
    Attached Images
      
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by karmacrunch)
    Hi!
    This kind of problem confuses me. For this particular one, I have the mark scheme but I don't understand why you have to do each step.

    Could someone go through how you would do this question, why you do each step? + Help me outline a way of tackling them.

    Thank you!
    Different methods. Here's one way:

    From the question we know that 3 bricklayers can build 18 walls in 15 days. We can write this as a ratio to make things simpler:

    3B : 18W : 15D

    There are 5 days left and they need to build 19 walls (37 - 18). So we need to know how many bricklayers are needed to build 19 walls in 5 days. Looking back at the original ratio

    3B : 18W : 15D

    First lets change the number of days from 15 to 5. If the number of days decreases by a factor of 3 then it makes sense that we will require 3 times the amount of bricklayers to do this work since they have less time to do the work. So now we have

    9B : 18W : 5D

    So it will take 9 bricklayers 5 days to build 18 walls. We're nearly there but we need to know how many bricklayers are needed to build 19 walls in the same time period.

    Can you carry on from here? Post your working/ideas if you get stuck.
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by karmacrunch)
    ...
    Out of interest, where did you get this question from?
    • Study Helper
    • Thread Starter
    Offline

    20
    ReputationRep:
    Study Helper
    I'm looking through your reply now, thanks!

    (Original post by notnek)
    Out of interest, where did you get this question from?
    It's an AQA GCSE Applications Unit 1 question. June 2012. (:
    • Study Helper
    • Thread Starter
    Offline

    20
    ReputationRep:
    Study Helper
    (Original post by notnek)
    Different methods. Here's one way:

    From the question we know that 3 bricklayers can build 18 walls in 15 days. We can write this as a ratio to make things simpler:

    3B : 18W : 15D

    There are 5 days left and they need to build 19 walls (37 - 18). So we need to know how many bricklayers are needed to build 19 walls in 5 days. Looking back at the original ratio

    3B : 18W : 15D

    First lets change the number of days from 15 to 5. If the number of days decreases by a factor of 3 then it makes sense that we will require 3 times the amount of bricklayers to do this work since they have less time to do the work. So now we have

    9B : 18W : 5D

    So it will take 9 bricklayers 5 days to build 18 walls.We're nearly there but we need to know how many bricklayers are needed to build 19 walls in the same time period.

    Can you carry on from here? Post your working/ideas if you get stuck.
    Ooh...

    9B : 18W : 5D
    ?B : 19W : 5D

    19/18= 1.0555... 1.0555... * 9= 9.5
    so ?= 9.5

    9.5-3= 6.5 <- but you have to round up 7.

    See, I understand it now but if that comes up in my exam, I'm not sure I will be able to see it immediately. :/
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by karmacrunch)
    Ooh...

    9B : 18W : 5D
    ?B : 19W : 5D

    19/18= 1.0555... 1.0555... * 9= 9.5
    so ?= 9.5

    9.5-3= 6.5 <- but you have to round up 7.

    See, I understand it now but if that comes up in my exam, I'm not sure I will be able to see it immediately. :/
    Which specific part are you not confident with?

    Try writing problems like this as 3 variable ratios and manipulating them. With 3 variable ratios you can keep one variable constant and change the other two.

    E.g. 3B : 18W : 15D

    We could keep the number of walls constant and double the number of builders. This will mean we need fewer days:

    6B : 18W : 7.5D

    Or we could keep the number of builders constant and double the number of walls. This will mean we need more days:

    3B : 36W : 30D

    Try this with different questions. If you practice then you'll be fine
    • Study Helper
    • Thread Starter
    Offline

    20
    ReputationRep:
    Study Helper
    (Original post by notnek)
    Which specific part are you not confident with?

    Try writing problems like this as 3 variable ratios and manipulating them. With 3 variable ratios you can keep one variable constant and change the other two.

    E.g. 3B : 18W : 15D

    We could keep the number of walls constant and double the number of builders. This will mean we need fewer days:

    6B : 18W : 7.5D

    Or we could keep the number of builders constant and double the number of walls. This will mean we need more days:

    3B : 36W : 30D

    Try this with different questions. If you practice then you'll be fine
    Thank you!
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    What's your favourite Christmas sweets?
    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
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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