Hey there Sign in to join this conversationNew here? Join for free

GCSE Maths help: Upper bounds and lower bounds

Announcements Posted on
Study Help needs new mods! 14-04-2014
We're up for a Webby! Vote TSR to help us win. 10-04-2014
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    Hi, I was wondering how to work out the upper and lower bound of numbers rounded to the nearest ____

    with ___ being: 1 decimal, 2 decimal, different no. of significant figures, nearest 10s, 100s, and any other rounding types you can think of that may appear on GCSE maths exams.
    (For example a question might say:
    Katie ran 5682 km rounded to the nearest ___ (km in this case but could be decimal place, sig. fig. and many other types). Work out the upper and lower bound of this.

    Can someone please post a number and show me what the upper bound and lower bound is to it in the forms (e.g. 3 sig. fig) and also explain to me how I would do it with any other number.

    I can kinda do rounded to nearest 1 or 2 decimal place but some are hard just as hundreth of a second or some sig figs AND ANY OTHER types of ways numbers may be rounded in..

    I can do: Find the upper bound of 6.8 rounded to 1 decimal place. = 6.85
    just the harder ones which don't ask for decimal places are a bit tricky...

    By the way, this is for the calculator GCSE paper.

    Thank you
    • 0 followers
    Offline

    ReputationRep:
    (Original post by Princestia)
    Hi, I was wondering how to work out the upper and lower bound of numbers rounded to the nearest ____

    with ___ being: 1 decimal, 2 decimal, different no. of significant figures, nearest 10s, 100s, and any other rounding types you can think of that may appear on GCSE maths exams.
    (For example a question might say:
    Katie ran 5682 km rounded to the nearest ___ (km in this case but could be decimal place, sig. fig. and many other types). Work out the upper and lower bound of this.

    Can someone please post a number and show me what the upper bound and lower bound is to it in the forms (e.g. 3 sig. fig) and also explain to me how I would do it with any other number.

    I can kinda do rounded to nearest 1 or 2 decimal place but some are hard just as hundreth of a second or some sig figs AND ANY OTHER types of ways numbers may be rounded in..

    I can do: Find the upper bound of 6.8 rounded to 1 decimal place. = 6.85
    just the harder ones which don't ask for decimal places are a bit tricky...

    By the way, this is for the calculator GCSE paper.

    Thank you
    add 0.5 for upper bound and minus 0.5 for lower bound. post a question next time not an essay. thanks, its too much to read.
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    (Original post by 130ss)
    add 0.5 for upper bound and minus 0.5 for lower bound. post a question next time not an essay. thanks, its too much to read.
    Yeah adding/minus 0.5 only works for certain types e.g. rounded to 1 decimal place doesn't it? It doesn't work for all cases.. I think..
    Lol sorry.. I can never be concise and I just wanted to be clear so I people won't be saying: "huh? What??" or replying about something that I don't mean lol...
    thanks anyway though
    • 0 followers
    Offline

    ReputationRep:
    (Original post by Princestia)
    Yeah adding/minus 0.5 only works for certain types e.g. rounded to 1 decimal place doesn't it? It doesn't work for all cases.. I think..
    Lol sorry.. I can never be concise and I just wanted to be clear so I people won't be saying: "huh? What??" or replying about something that I don't mean lol...
    thanks anyway though
    add or minus .5 after the decimal. if the question is upper bound of 8 = 8.5
    upper bound of 8.4 =8.45
    its hard to explain
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    (Original post by 130ss)
    add or minus .5 after the decimal. if the question is upper bound of 8 = 8.5
    upper bound of 8.4 =8.45
    its hard to explain
    lol thanks.. yeah i do get what you mean.. but I mean what if it's a number that doesn't contain a decimal point and the question says it's rounded to the nearest hundredth or something like that? I'm sure the answer would not be to 0.5 for the upper bound and minus 0.5 for the lower bound..
    Thanks for posting again though
    • 1 follower
    Offline

    ReputationRep:
    (Original post by Princestia)
    lol thanks.. yeah i do get what you mean.. but I mean what if it's a number that doesn't contain a decimal point and the question says it's rounded to the nearest hundredth or something like that? I'm sure the answer would not be to 0.5 for the upper bound and minus 0.5 for the lower bound..
    Thanks for posting again though
    I understand what you're saying. Basically if its nearest hundreth, go to the thousands and +-5 thousandths. Its easier to explain with numbers then words is think.

    So

    0.5 = 0.45 - 0.55
    0.65 = 0.645 - 0.655
    0.7663 = 0.76625 - 0.76635

    So you're basically going one extra place and adding +- 5 of that, hopefully you get what I mean.

    Sometimes you might get for example

    630 is accurate to the nearest 10, what is the upper and lower bound?

    As its nearest 10, go to hundreds and do +- 5, so that would be 625 - 635.

    Hopefully that's clear, someone else will probably be able to explain it better.
    • 0 followers
    Offline

    ReputationRep:
    (Original post by Princestia)
    lol thanks.. yeah i do get what you mean.. but I mean what if it's a number that doesn't contain a decimal point and the question says it's rounded to the nearest hundredth or something like that? I'm sure the answer would not be to 0.5 for the upper bound and minus 0.5 for the lower bound..
    Thanks for posting again though
    image a number with no decimal, jut imagine that at the end of a number it has a decimal. so 145 = 145. or 174395 = 174395.
    then just use this rule.
    • 5 followers
    Offline

    ReputationRep:
    10.52-
    Is the lower bound 10.515 and the upper bound 10.525?
    • 7 followers
    Offline

    ReputationRep:
    (Original post by the don)
    10.52-
    Is the lower bound 10.515 and the upper bound 10.525?
    yes
    • 11 followers
    Offline

    ReputationRep:
    (Original post by Princestia)
    Hi, I was wondering how to work out the upper and lower bound of numbers rounded to the nearest ____

    with ___ being: 1 decimal, 2 decimal, different no. of significant figures, nearest 10s, 100s, and any other rounding types you can think of that may appear on GCSE maths exams.
    (For example a question might say:
    Katie ran 5682 km rounded to the nearest ___ (km in this case but could be decimal place, sig. fig. and many other types). Work out the upper and lower bound of this.

    Can someone please post a number and show me what the upper bound and lower bound is to it in the forms (e.g. 3 sig. fig) and also explain to me how I would do it with any other number.

    I can kinda do rounded to nearest 1 or 2 decimal place but some are hard just as hundreth of a second or some sig figs AND ANY OTHER types of ways numbers may be rounded in..

    I can do: Find the upper bound of 6.8 rounded to 1 decimal place. = 6.85
    just the harder ones which don't ask for decimal places are a bit tricky...

    By the way, this is for the calculator GCSE paper.

    Thank you
    Examples of lower and upper bounds:

    15 to the nearest 5.
    UB = 17.5
    LB = 12.5

    320 to 2 sig fig.
    UB = 325
    LB = 315

    2.34 to 2 decimal places.
    UB = 2.345
    LB = 2.335

    You just need to know how to find the lower and upper bounds of numbers and then use that to answer questions.

Reply

Submit reply

Register

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?

    this is what you'll be called on TSR

  2. this can't be left blank
    this email is already registered. Forgotten your password?

    never shared and never spammed

  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. By completing the slider below you agree to The Student Room's terms & conditions and site rules

  2. Slide the button to the right to create your account

    Slide to join now Processing…

    You don't slide that way? No problem.

Updated: May 31, 2011
Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.