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Intern
Joined: 13 Sep 2006
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Quantitative Question [#permalink]
 14 Sep 2006, 09:42
I can't figure the following questions out:
1) For all real numbers v, the operation V* is defined by the equation V*=V-V/3. If (V*)*=8, the v=
A)15
B)18
C)21
D)24
E)27
The answer happens to be B)18
2) A rectangular tabletop consists of a pice of laminated wood bordered by a thin metal strip along its four edges. The surface area of the tabletop is x square feet, and the total length of the strip before it was attached was x feet. If the tabletop is 3 feet wide, what is its approximate length, in feet?
A)12
B)10
C)9
D)8
E)6
The answer is B)10
Can someone explain these answers to me.
Thanks!
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SVP
Joined: 05 Jul 2006
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For the first one My ANSWER IS B
fisrst simplifyv* = v-v/3 = 2/3v name it b thus v* = b =2/3v
(v*)* = b* = 2/3b = 2/3(2/3v) = 4/9v
given that (v*)* = 8
thus 4/9v = 8 therfore v = 18
for the second one
i think
area of table top = circomference = x
ie 2l+2w = lw = x and given w=3
thus 2l+3*2 = 3l ie l =6
it is not 10 as mentioned but this is the best i could get
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Senior Manager
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hmmm
for #2 I get E)6:
w=3 so l had to be x/3 for area to = x
2x3 + 2(x/3) = x (perimetar is also x)
x/3 = 6
x=18
length = 18/3 = 6
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SVP
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Is it just me? Cause I think some of these problem solving questions are just poorly worded. I didn't understand the problem until I saw how above posters tried to solve it.
So basically, it's asking for what value of the length(x/3) does the perimeter equal the area?
If so, it clearly can't be 10 because A=30 and P=26, not a very good approximation.
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Intern
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Quantitative Question [#permalink]
14 Sep 2006, 13:48
Thanks for all your help!
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Manager
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[quote="EconGirl"]hmmm
for #2 I get E)6:
w=3 so l had to be x/3 for area to = x
2x3 + 2(x/3) = x (perimetar is also x)
x/3 = 6
x=18
length = 18/3 = 6[/quote]
I am also getting 6.
Area = x
Length of strip = x
Width = 3
Perimeter = 2L + 2W
2W = 6
L = (Length of metal strip - 2W) / 2
= (x - 6 ) / 2
Area = width * length
x = 3 * (x-6)/2
2x = 3(x-6)
2x = 3x - 18
x = 18
Since area is 18 and we know width is 3
Length = x / 3
= 18/3
= 6
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Director
Joined: 23 Jun 2005
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Agree with Yezz and others on the second one - the answer is 6 E
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VP
Joined: 02 Jun 2006
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Try and simplify the problem first
V* = V-V/3 = (3V-V)/3
= 2V/3
Now,
(V*)* = (2V/3)*
=2V/3 - (2V/3)/3
=2V/3 - 2V/9
= 6V/9 - 2V/9
= 4V/9 = 8
=> V = 18.
Second one is 6 too... so OA is wrong.
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