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Manager
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In a certain business, production index p is directly [#permalink]
 15 Jun 2006, 01:16
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In a certain business, production index p is directly proportional to efficiency index e, which is in turn directly proportional to investment index i. What is p if i=70?
condition 1: e = 0.5 whenever i = 60.
condition 2: p = 2.0 whenever i = 50.
Please explain the rationale behind your answer choice. Thanks.
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GMAT Club Legend
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p = ae
e = bi
so p=abi
St1:
p = abi
i = 60, e = 0.5, so the factor b must be 1/120. If i = 70, e = 7/12. We can't solve as we cannot derive the factor a.
St2:
p = abi
2 = (a)(b)(50)
ab = 2/50 = 1/25
So if i = 70, p = abi = (1/25)(70). Sufficient.
Ans B
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Director
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clearly B.
stmt 1 --insuff gives us no data on how e and i are related
stmt 2-- gives us that relation , basically , (70*2)/50=2.8
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Manager
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ywilfred wrote: p = ae
e = bi
so p=abi
St1:
p = abi
i = 60, e = 0.5, so the factor b must be 1/120. If i = 70, e = 7/12. We can't solve as we cannot derive the factor a.
St2:
p = abi
2 = (a)(b)(50)
ab = 2/50 = 1/25
So if i = 70, p = abi = (1/25)(70). Sufficient.
Ans B
Great! thanks for the explanation. A quick question, so when they say directly proportional, just sub any variable "a" into the equation.
p = ae
e = bi
a,b are just random variables assigned to represent the proportional relationship btw p and e and e and i.
Just want to make sure.
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Director
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Yes, but you're better off not calling them variables a and b, but denoting them as constants K1, K2 etc....just to avoid confusion.
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GMAT Club Legend
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mrmikec wrote: ywilfred wrote: p = ae
e = bi
so p=abi
St1:
p = abi
i = 60, e = 0.5, so the factor b must be 1/120. If i = 70, e = 7/12. We can't solve as we cannot derive the factor a.
St2:
p = abi
2 = (a)(b)(50)
ab = 2/50 = 1/25
So if i = 70, p = abi = (1/25)(70). Sufficient.
Ans B Great! thanks for the explanation. A quick question, so when they say directly proportional, just sub any variable "a" into the equation. p = ae e = bi a,b are just random variables assigned to represent the proportional relationship btw p and e and e and i. Just want to make sure. yes, I used a and b to represent the proportional constant. you can use anything you like, so long as it doesn't confuse you =)
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Manager
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B aswell
stmt 1 does not give the ratio between p and i
stmt 2 does.
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SVP
Joined: 30 Mar 2006
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Cleary B
P = xe and e =yi
Hence p= xyi
1) e = 0.5 when i =60 But we still don't know x
Henc insuff
2) p =2 when i = 50
Hence p = 2/50 * 70 , when i = 70
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Director
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Point to be kept in mind here is -
If x proportional to y and y proportional to z, then x is also proportional to z.
Answer is B.
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CEO
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Straight B.
p is directly proportional to e and e is directly proportional to i. So p is directly proportional to i.
_________________
SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008
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