Plugging-in question from princeton

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Plugging-in question from princeton

by reddox » Fri Aug 10, 2012 7:58 pm
Struggling with this 'Plugging-in' Q-type from a Princeton course;

The juice stall at the circus stocked just 2 brands of orange tetra-packs. Brand 'A' cost $1 per pack & Brand 'B' cost $1.5 per pack. Last week, Brand 'A' contributed to 'm'% of the stall's revenue and accounted for 'n'% of the sales of tetra-packs.

Which of the following expresses 'm' in terms of 'n'?

A. 100n/(150-n)
B. 200n/(250-n)
C. 200n/(300-n)
D. 250n/(400-n)
E. 300n/(500-n)
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Gopi A.

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by Birottam Dutta » Fri Aug 10, 2012 8:34 pm
Its best to assume numbers and solve this one.

Let number of tetra-packs of A and B sold be 10 each.

So, n = 10/20 = 50%.

Revenue generated from A = $10 and from B = $15.

So, m = 10/(10+15) = 10/25 = 40%.

Now, go by options by putting n into each of the options and checking value of m.

A 100n/(150-n) = 100*50/(150-50) = 50%. Not correct.
B 200n/(250-n) = 200*50/(250-50) = 50%. Not correct.
C 200n/(300-n) = 200*50/(300-50) = 40%. Correct.

Check the other two options as well.

Answer though as shown above is C!

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by reddox » Sat Aug 11, 2012 9:17 am
Thanks for that! I was confused with n '%' and m '%'. Because I was thinking in terms of '%', I ended up trying to convert my plugged-in values to non-percent integers. :(

Any tip on thinking with more clarity?
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Gopi A.