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# In a certain business, production index p is directly

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Manager
Joined: 17 Dec 2005
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In a certain business, production index p is directly [#permalink]  15 Jun 2006, 00:16
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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.

GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5078
Location: Singapore
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Kudos [?]: 184 [0], given: 0

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
Director
Joined: 26 Sep 2005
Posts: 578
Location: Munich,Germany
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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
Manager
Joined: 17 Dec 2005
Posts: 162
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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.
Director
Joined: 28 Dec 2005
Posts: 758
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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.
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5078
Location: Singapore
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Kudos [?]: 184 [0], given: 0

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 =)
Manager
Joined: 14 Mar 2006
Posts: 209
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B aswell

stmt 1 does not give the ratio between p and i
stmt 2 does.
SVP
Joined: 30 Mar 2006
Posts: 1739
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Kudos [?]: 46 [0], given: 0

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
Director
Joined: 06 May 2006
Posts: 781
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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.

CEO
Joined: 20 Nov 2005
Posts: 2913
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
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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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