# Maths question help

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

1. ### zee210New 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_ShedOccasional 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. ### zee210New commenter

Thank you for your response

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4. ### briancantOccasional 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. ### zee210New 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!

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6. ### gnulinuxOccasional 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. ### briancantOccasional commenter

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