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DS - Set 25 Math

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f2001290: Master | Next Rank: 500 Posts; Posts: 400; Joined: Sat Mar 10, 2007 4:04 amFollowed by: 1 member; Thanked: 1 times

by f2001290 » Tue Jun 12, 2007 1:43 pm

If the average (arithmetic mean) of the assessed values
of x houses is $212,000 and the average of the assessed
values of y other houses is $194,000, what is the average
of the assessed values of the x+y houses?
(1) x+y=36
(2) x=2y

I chose B, but surprisingly it turned out to be C. Clueless:)

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Source: Beat The GMAT — Data Sufficiency | Tue Jun 12, 2007 1:43 pm

mschling52: Master | Next Rank: 500 Posts; Posts: 105; Joined: Mon Sep 18, 2006 12:34 pm; Location: OH; Thanked: 7 times; GMAT Score:780

by mschling52 » Thu Jun 14, 2007 9:04 am

I agree with you...I think it's B

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simplythebest: Junior | Next Rank: 30 Posts; Posts: 22; Joined: Mon Sep 18, 2006 10:17 am

by simplythebest » Thu Jun 14, 2007 10:36 pm

I think the answer should be C.

WE need

($212,000*x + $194,000y) / x + y

and only with both the statements we can exactly find the assessed values of X+Y

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mschling52: Master | Next Rank: 500 Posts; Posts: 105; Joined: Mon Sep 18, 2006 12:34 pm; Location: OH; Thanked: 7 times; GMAT Score:780

by mschling52 » Fri Jun 15, 2007 4:46 am

You are right, that is the formula we need to solve, but if we know just (2) then that formula becomes

(212,000(2y) + 194,000y)/((2y)+y)

= (618,000y)/(3y) = 206,000

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simplythebest: Junior | Next Rank: 30 Posts; Posts: 22; Joined: Mon Sep 18, 2006 10:17 am

by simplythebest » Fri Jun 15, 2007 5:25 am

Grr..Silly mistake...yup...It should be B...think i should write "Read questions carefully" a 1000 times imposition..

Thanks Mate !!!

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