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# An oculist charges $30 for an eye examination, frames, and  Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: Current Student Joined: 29 Jan 2005 Posts: 5244 Followers: 23 Kudos [?]: 178 [0], given: 0 An oculist charges$30 for an eye examination, frames, and [#permalink]  17 Oct 2005, 05:40
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An oculist charges $30 for an eye examination, frames, and glass lenses, but$40 for for an eye examination, frames, and plastic lenses. If the plastic lenses cost four times as much as the glass lenses, how much do the glass lenses cost?

Why do I keep getting the wrong answer $3? Current Student Joined: 28 Dec 2004 Posts: 3391 Location: New York City Schools: Wharton'11 HBS'12 Followers: 13 Kudos [?]: 180 [0], given: 2 [#permalink] 17 Oct 2005, 05:50 well lets see... E+F+G=30 E+F+P=40 p=4G two simeltaneous equations. you get 3g=10, g=$3.33
Current Student
Joined: 29 Jan 2005
Posts: 5244
Followers: 23

Kudos [?]: 178 [0], given: 0

I got $3, but we are both wrong according to the OA. Senior Manager Joined: 02 Oct 2005 Posts: 303 Followers: 1 Kudos [?]: 7 [0], given: 0 [#permalink] 17 Oct 2005, 07:29 fresinha12 wrote: GMATT73 wrote: I got$3, but we are both wrong according to the OA.

It should be $4 I also got 3.33 . How could we get 4? Pls explain also what is OA? Current Student Joined: 28 Dec 2004 Posts: 3391 Location: New York City Schools: Wharton'11 HBS'12 Followers: 13 Kudos [?]: 180 [0], given: 2 [#permalink] 17 Oct 2005, 07:36 well...it has to be 3.33...I have no idea why that is no the OA... sudhagar wrote: fresinha12 wrote: GMATT73 wrote: I got$3, but we are both wrong according to the OA.

It should be $4 I also got 3.33 . How could we get 4? Pls explain also what is OA? Current Student Joined: 29 Jan 2005 Posts: 5244 Followers: 23 Kudos [?]: 178 [0], given: 0 [#permalink] 17 Oct 2005, 07:50 From the Kaplan Math book (Pg. 87): OA is$4

OE

In each case the examination and the frames are the same; the difference in cost must be due to a difference in the costs of the lenses. Since plastic lenses cost 4 times as much as glass lenses, the difference in cost must be 3 times the cost of the glass lenses.

Difference in cost=Cost of plastic-cost of glass
=4-1
=3

The difference in cost is $42-30; or$12. Since this is 3 times the cost of the glass lenses, the glass lense must cost $12/3=$4.
Current Student
Joined: 28 Dec 2004
Posts: 3391
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 180 [0], given: 2

how did the cost become $42? I thought you posted cost to be$40

GMATT73 wrote:
From the Kaplan Math book (Pg. 87):