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Can anyone explain that maths question?

In the edexcel 9-1 paper, there was a question to do with squares, circles and colours. How did you guys find the answer and what was the question to begin with? I had no idea

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Original post by That'sGreat
In the edexcel 9-1 paper, there was a question to do with squares, circles and colours. How did you guys find the answer and what was the question to begin with? I had no idea

do you remember the ratios?
Original post by CraigBackner
do you remember the ratios?


3:7 (white shapes to black shapes) 4:5 (white circles to white squares) 2:5 (black circles to black square). What fraction of circles are there, give answer in a fraction. ----- that was the question i think and those were the ratios. Apparently something to do with equivalent ratios or something
Original post by That'sGreat
3:7 (white shapes to black shapes) 4:5 (white circles to white squares) 2:5 (black circles to black square). What fraction of circles are there, give answer in a fraction. ----- that was the question i think and those were the ratios. Apparently something to do with equivalent ratios or something


What I did (probably wrong) was to do probability trees - so 3/10 are white and 4/9 are circles so thats 12/90 white circles etc..
Original post by That'sGreat
3:7 (white shapes to black shapes) 4:5 (white circles to white squares) 2:5 (black circles to black square). What fraction of circles are there, give answer in a fraction. ----- that was the question i think and those were the ratios. Apparently something to do with equivalent ratios or something


i let the total shapes 630 and then worked it out from there but in the exam i got 3/5 which is wrong it should be 1/3
Reply 5
Original post by That'sGreat
In the edexcel 9-1 paper, there was a question to do with squares, circles and colours. How did you guys find the answer and what was the question to begin with? I had no idea

Here's the question:

White shapes and black shapes are used in a game.
Some of the shapes are circles.
All the other shapes are squares.

The ratio of the number of white shapes to black shapes is 3:7
The ratio of the number of white circles to white squares is 4:5
The ratio of the number of black circles to black squares is 2:5

Work out the fraction of all shapes that are circles.
(edited 6 years ago)
Reply 6
Original post by That'sGreat
In the edexcel 9-1 paper, there was a question to do with squares, circles and colours. How did you guys find the answer and what was the question to begin with? I had no idea

There are different ways to do it but I would use algebra by letting the number of white shapes = 3x then the number of black shapes must be 7x.

Then the total number of shapes is 10x.

And you can continue to work out the number of white circles, black circles, white squares and black squares in terms of x.

Then sum these to find the ratio of squares to circles.
take x as the whole number of shapes; (3/10)x is the number of white shapes,(7/10)x is the number of black shapes.Therefore the number of white circles is 4/9 * (3/10)x, and the number of black circles is 2/7*(7/10)x; you then add them together to get the total.(12/90)x (14/70)x, then the rest.
the "x" is not really necessary, it just makes the working out easier to read.
Original post by notnek
There are different ways to do it but I would use algebra by letting the number of white shapes = 3x then the number of black shapes must be 7x.

Then the total number of shapes is 10x.

And you can continue to work out the number of white circles, black circles, white squares and black squares in terms of x.

Then sum these to find the ratio of squares to circles.


can you explain how the answer is 1/3 because i keep getting 3/5 even using this method3
(edited 6 years ago)
Reply 10
Original post by CraigBackner
is the answer 3/5 because thats what i keep getting even using this method

No the answer is 1/3 . Please post your working.
Original post by CraigBackner
can you explain how the answer is 1/3 because i keep getting 3/5 even using this method3

even with my method?, i think the numbers may be wrong because i remember getting 1/3 in the exam.
I get 1/3 right now with my method, 12/90 + 14/70,
2/15+2/10
10/30:
Original post by dxpeguy
I get 1/3 right now with my method, 12/90 + 14/70,
2/15+2/10
10/30:


Where is 14/70 from? I thought its 7/10 x 2/10, so 14/100
Original post by dxpeguy
I get 1/3 right now with my method, 12/90 + 14/70,
2/15+2/10
10/30:


Nevermind, i misread the question
This is how I did the ratio question. Hope this helps:

Posted from TSR Mobile
Original post by notnek
No the answer is 1/3 . Please post your working.


would it work if i let the total shapes be 630 ?
Reply 17
Original post by CraigBackner
would it work if i let the total shapes be 630 ?

To me that method sounds fine. And I think it would get the marks looking at specimen mark schemes for similar questions, assuming the final answer was correct.

Of course it would be safer (in terms of getting the marks) to let the total be xx instead of an arbitrary number like 630 :smile:
(edited 6 years ago)
Anyone remeber what the simultaneous equation q was? if so lmk please
white circles is 3:10 x 4:9 = 12:90Black circles is 7:10 x 2:7 = 14:7012:90 14:70 = 2:15 1:52:15 3:15 = 5:15 = 1:3

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