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GCSE Maths question - Help...?

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stamina9008
stamina9008 Posts: 319 Forumite
edited 28 December 2012 at 11:00PM in Student MoneySaving
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«13

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  • Own_My_Own
    Own_My_Own Posts: 6,098 Forumite
    Xmas Saver!
    Hi, my dad uses this site but i thought it might be a good place to ask this question..
    Please help me answer it, it's part of my homework and i cant understand it..
    I dont think the answer is 3/5, so..please help..

    4. Challenge!
    Simon ate 1/5 of a cake and his sister ate 1/4 of what was left.
    What fraction of the cake is now left? (hint: a diagram may help!)

    I understand the four rules of fractions, but this question is really annoying me..

    Have a nice day

    I would say 3/5 were left. But then I left school over 20 years ago.

    If Simon ate 1/5 he left 4/5 or 4 pieces. If his sister ate 1/4 of this , she ate 1 piece, leaving 3 pieces or 3/5.
  • That's what i think, im just looking for assurance really.

    Let's see if were right, hopefully a maths boffin comes along, cos im certainly not one..lol

    Yeah - - It probably is 3/5 'OwnMyOwn', thanks.
  • mrcow
    mrcow Posts: 15,170 Forumite
    Part of the Furniture 10,000 Posts Combo Breaker
    So he ate 1/5 : or 4/20

    So there were 16/20 left.

    She ate 1/4 of that : or 4/20

    So there are 12/20 left or 3/5 simplified.
    "One day I realised that when you are lying in your grave, it's no good saying, "I was too shy, too frightened."
    Because by then you've blown your chances. That's it."
  • whitewing
    whitewing Posts: 11,852 Forumite
    Part of the Furniture 10,000 Posts Combo Breaker
    5/5 minus 1/5 is 4/5 of the cake left after the brother eats a piece.

    4/4 minus 1/4 is 3/4 left after sister eats a piece.

    3/4 times 4/5 is 3/5.

    of = times in maths vocab.
    :heartsmil When you find people who not only tolerate your quirks but celebrate them with glad cries of "Me too!" be sure to cherish them. Because these weirdos are your true family.
  • mrcow
    mrcow Posts: 15,170 Forumite
    Part of the Furniture 10,000 Posts Combo Breaker
    PS. I'm a maths boffin ;)
    "One day I realised that when you are lying in your grave, it's no good saying, "I was too shy, too frightened."
    Because by then you've blown your chances. That's it."
  • It's easier to see if you put it into hundredths (not quite percentages per se)

    The cake is 100 pieces.

    Simon eats a fifth, which is 20 pieces. So there's 80 pieces left.

    The sister eats a quarter of what's left. So out of the 80 pieces, she eats 20. Same as Simon. Their family definitely have the 'one cuts and the other one chooses' rule.

    So there's 60 pieces left out of the original 100, which is 60/100, 6/10, 3/5.

    If you were doing it as a diagram, a pie chart would be best (honestly!)
    "Most of the people ... were unhappy... Many solutions were suggested for this problem, but most of these were largely concerned with the movements of small green pieces of paper, which is odd because on the whole it wasn't the small green pieces of paper that were unhappy." -- Douglas Adams
  • PHYTHIAN
    PHYTHIAN Posts: 339 Forumite
    Ninth Anniversary Combo Breaker
    Yep...3/5
    Simon eats 1/5 so 4/5 left
    Always subsistute 'of' for 'times by'. So 1/4 of 4/5 is the same as
    1/4 x 4/5 = 4/20 = 1/5.
    So she eats 1/5 meaning 3/5 remain.
    Justice will not be served until those who are unaffected are as outraged as those affected (Benjamin Franklin) JFT96...YNWA
  • Dunroamin
    Dunroamin Posts: 16,908 Forumite
    Isn't anyone else shocked that a question like this is being set at GCSE level?
  • Anselm
    Anselm Posts: 7,009 Forumite
    Try to get access to https://www.mymaths.co.uk
    "Nothing, Lucilius, is ours, except time." - Seneca
    Moral letters to Lucilius/Letter 1
  • foofi22
    foofi22 Posts: 2,209 Forumite
    Part of the Furniture 1,000 Posts
    Dunroamin wrote: »
    Isn't anyone else shocked that a question like this is being set at GCSE level?

    Yep, this is more A Level
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