the whole sweet siuation is irrelevant as is the 1/3 odds of her picking out 2 of the same colour. just take the equasion and reverse it. you know u have to subtract the 90 at the end to = 0 so u know that N^2 - N = 90 so its simply a case of finding which number fits, even if it isnt obvious straight away u could quite simply just work ur way through each number until u find the one that works.
i think if they had asked the question without the silly girl and her sweets this wouldnt of been brought up. simple question IMO, but then again i always did like maths
A question is always very simple if you give the answer you want...instead of answering the actual questions lol. The real question for me is ....what happened the rest of the sweets! Posted by gerardirl
To further explain, bearing in mind I'm just a grunt.. There are six orange sweets in the bag, so the odds of picking the first orange sweet is 6 divided by the number of sweets. We don't know that figure, so it's called 'N' (or x or y or z or anything). The chances of picking a second sweet are now five (one orange sweet less) divided by the number of sweets left in the bag, which is the total minus the one taken out (i.e. N-1) To get the chances for both sweets being orange, which are co-dependent, the chances are multiplied together. The top and bottom lines are multiplied separately. This gives 6*5 divided by N*(N-1). Worked out is 30 divided by N^2-N We are told the probability is 1/3. Therefore 30/N^2-N = 1/3 Multiply both sides of the equation by N^2 - N , to simplify. This changes to 30 = N^2-N/3 Multiply both sides of the equation by 3, to simplify further. This gives 90 = N^2-N To get one side of the equation to equal zero, subtract 90 from both sides. This gives 0 = N^2-N - 90 Hope that clears it up. Posted by Benchmark
One of my friends posted this question on FB and I have to admit I plagiarised your work to look smarter than I am.
To further explain, bearing in mind I'm just a grunt.. There are six orange sweets in the bag, so the odds of picking the first orange sweet is 6 divided by the number of sweets. We don't know that figure, so it's called 'N' (or x or y or z or anything). The chances of picking a second sweet are now five (one orange sweet less) divided by the number of sweets left in the bag, which is the total minus the one taken out (i.e. N-1) To get the chances for both sweets being orange, which are co-dependent, the chances are multiplied together. The top and bottom lines are multiplied separately. This gives 6*5 divided by N*(N-1). Worked out is 30 divided by N^2-N We are told the probability is 1/3. Therefore 30/N^2-N = 1/3 Multiply both sides of the equation by N^2 - N , to simplify. This changes to 30 = N^2-N/3 Multiply both sides of the equation by 3, to simplify further. This gives 90 = N^2-N To get one side of the equation to equal zero, subtract 90 from both sides. This gives 0 = N^2-N - 90 Hope that clears it up. Posted by Benchmark
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you know u have to subtract the 90 at the end to = 0
so u know that N^2 - N = 90 so its simply a case of finding which number fits, even if it isnt obvious straight away u could quite simply just work ur way through each number until u find the one that works.
i think if they had asked the question without the silly girl and her sweets this wouldnt of been brought up. simple question IMO, but then again i always did like maths
btw the answer is 10
;o)