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Maths question help

Discussion in 'Mathematics' started by zee210, Dec 10, 2018.

  1. zee210

    zee210 New commenter

    Hi

    If three solids A, B and C are similar, wouldn't the ratio of lengths be the same between A and B and B and C?

    I'm confused by question 15 in Edexcel Nov 2018 H paper 1 if anyone can explain this to me that would be great.

    Thanks
     
  2. Maths_Shed

    Maths_Shed Occasional commenter

    Square root the ratio of areas to find the ratio of lengths, cube root the ratio volumes to find a different ratio of lengths and then find A:B:C
     
  3. zee210

    zee210 New commenter

    Thank you for your response
     
    Maths_Shed likes this.
  4. briancant

    briancant Occasional commenter

    This style of question is becoming fairly standard. I wonder what you though of the second to last questions on vectors on this paper? I thought it was one of the hardest I've seen at GCSE level and would expect only one in several hundred students to score full marks on it.
     
  5. zee210

    zee210 New commenter

    I thought that question was horrible! Another colleague had to explain it to me as I didn't understand where they got the multiple from in the mark scheme/pupil friendly mark scheme!
    Poor students!
     
    briancant likes this.
  6. gnulinux

    gnulinux Occasional commenter

    The short answer is no! There is no such thing as a 'ratio of lengths'. If A B and C are 'solid' shapes and 'similar' then there has to be a 'meaningful' correspondence between the significant parts of these shapes so that they are essentially the 'same shape' apart from 'size'.

    The ratio of corresponding dimensions between A and B is a fixed quantity and can be anything, as can the ratio of corresponding dimensions between B and C.
     
  7. briancant

    briancant Occasional commenter

    Eh! I thought I understood the question but I don't understand your response gnulinux!
     

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