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This problem single handedly screwed my quant section this week. I can't remember the exact numbers involved, but it was something like:

'n' parents split the $300 cost of a school trip equally. If the school had three less parents, each the parents would each pay an additional $3. Find 'n'

my method was... 300/n = x 300 = nx

and

300/n-3 = x +3 300 = nx + 3n - 3x - 9 sub nx = 300 300 = 300 + 3n - 3x - 9 9 = 3(n - x) 3 = n - x .... then I don't know, not sure if I'm even doing this right. I think it was just jitters, but i spent 5 full minutes on this and finally just guessed.

My question is: what's the correct method here and has anyone seen a question similar to this so I can work it out with numbers that actually add up? This seems really easy but I'm just not getting something and it's driving me insane. Thanks!

Approach is right.. some data is wrong as solving it is leading to irrational roots. To correct data, let n decreases by 5 and x increases by 5, then we get 5 = n-x by your approach (instead of 3= n-x)

Next step is to put x= n-5 in the equation nx=300 , solve quadratic equation to get n = 20 and x =15

Approach is right.. some data is wrong as solving it is leading to irrational roots. To correct data, let n decreases by 5 and x increases by 5, then we get 5 = n-x by your approach (instead of 3= n-x)

Next step is to put x= n-5 in the equation nx=300 , solve quadratic equation to get n = 20 and x =15

Feel free to write if you have any further queries.

Cheers! Neha Singh

Thanks Neha!!! I think on the actual test the problem was that I wasn't resubbing after the first substitution in order to get a quadratic and solve that way. I'm used to two variable/two equation problems being a little more straightforward. Thanks for clarifying.

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