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Data Sufficiency

by dassabyasachi14 » Wed May 25, 2016 7:02 pm
If the ratio of no. of teachers to the no. of students is the same in school district M and School district P, what is the ratio of the number of students in school district M to the no f students in School district P?

1) There are 10, 000 more students in school district M than there are in school District P.

2) The ratio of the number of teachers to the no. of students in school district M is 1 to 20.

Please help me out how to solve this question. Official answer E.


As per me the answer should be B. Can anyone please explain.
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by [email protected] » Thu May 26, 2016 9:21 am
Hi dassabyasachi14,

There's a full discussion of this question here:

https://www.beatthegmat.com/teacher-to-s ... 74429.html

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Rich
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by Matt@VeritasPrep » Thu May 26, 2016 2:40 pm
Say there are x teachers and y students in M and a teachers and b students in P. We want y / b.

The prompt gives us x/y = a/b, so we've got something to start with.

S1:

y = b + 10,000

Obvs not a ratio, so not sufficient.

S2:

x/y = 1/20, or x = 20y. This also tells us that a/b = 1/20, so a = 20b. This doesn't help us with y/b, though! (To illustrate, say we have 1 teacher and 20 students in P. We could have the same (1 and 20) in M, or we could have 100 and 2000, so we can't solve.

S1 + S2:

We've got

y = b + 10,000
a/b = 1/20
x/y = 1/20

So our ratio y/b = (b + 10,000)/b ... but we can't solve for b!
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by dassabyasachi14 » Sat Jun 04, 2016 8:56 am
Thanks Rich and Matt!! :)
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