Question 2 (nov.24th)

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bacali
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Topic: Question 2 (nov.24th)
PostMon Nov 24, 2008 12:37 pm
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Q3:

Material A costs $3 per kilogram, and material B costs $5 per kilogram. If 10 kilograms of material K consists of x kilograms of material A and y kilograms of material B, is x > y?
(1) y > 4
(2) The cost of the 10 kilograms of material K is less than $40.


OA: B
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cramya
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PostMon Nov 24, 2008 2:09 pm
Given x+y=10

3x + 5y is the cost

Stmt I)

x could be 3 y could be 7

x<y

x could be 7 y could be 3

x>y

INSUFF

Stmt II

Given x+y=10 and
3x + 5y is the cost in question stem

x=10-y AND y=10-x

In stmt II its given that 3x+5y<40

Substitute X=10-Y

3(10-Y)+5Y < 40
30-3Y+5Y<40
2Y<10
Y<5

Since x+y=10 definitely x>y

SUFF

B)
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PostTue Oct 20, 2009 12:58 am
Quote:
Material A costs $3 per kilogram, and material B costs $5 per kilogram. If
10 kilograms of material K consists of x kilograms of material A and y
kilograms of material B, is x > y?
(1) y > 4
(2) The cost of the 10 kilograms of material K is less than $40.
OE says:
Since x + y = 10, the relation x > y is equivalent to
x > 10 - x, or x > 5.
(1) The given information is consistent with
x = 5.5 and y = 4.5, and the given
information is also consistent with ]x = y = 5.
Therefore, it is possible for x > y to be true
and it is possible for x > y to be false; NOT
sufficient.

How can we take the case of x = y = 5 when we know x>5??
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PostFri Nov 06, 2009 11:35 pm
yeah uptowngirl92, this is the same question that came to my mind.

We need explanation pls..
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PostSat Nov 07, 2009 4:06 am
cramya wrote:
Given x+y=10

3x + 5y is the cost

Stmt I)

x could be 3 y could be 7

x<y

x could be 7 y could be 3

x>y

cramya, I dont understand how x could be 7 and y could be 3 from statement 1 since its already given that y>4...can u pls explain.

This doesn't change the ans as you can still have x=y=5 in which case x<y is 'no' or x=3, y=7 in which case x<y is 'yes' but I just want to make sure I have interpreted it correctly.

thanks.
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PostSat Nov 07, 2009 8:26 pm
bacali wrote:
Q3:

Material A costs $3 per kilogram, and material B costs $5 per kilogram. If 10 kilograms of material K consists of x kilograms of material A and y kilograms of material B, is x > y?
(1) y > 4
(2) The cost of the 10 kilograms of material K is less than $40.
Another standard question that appears on GMAT in various guises.

Avg of A = 3, Avg of B = 5.

The mixture of 10 kgs costs $40.

The avg price of mixture < 4 which is less than (5+3)/2.


From this we can conclude that x < y.


Question in different guises.

You got a set of dimes and a set of quarters; and you are given a total of $13.50 with a total of 90 coins. Are the number of dimes greater than number of dimes.


Another disguise.


z lies in between 10 and y on a number line. Is the arithmetic mean of 10 and y greater than z.
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heshamelaziry
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PostMon Nov 09, 2009 5:00 pm
I understand the algebra solution by cramya. But if I try numbers, x can be less than or more than y.

Sad
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PostMon Nov 09, 2009 10:52 pm
answer is B. Reasoning is as follows:

From A, it states that y>4.

X+y=10..therefore if Y=5, X should be 5.. or if Y=6, X should be 4 ...From A, X can be equal to Y or can be less than Y..

Hence not sufficient..

From B, The cost of the 10 kilograms of material K is less than $40.

Therefore, 3X+5Y<40.. start inputting values for x and y..
Consider, X=3 and Y=7.. it crosses 40..not possible..

If X =5, Y=5, it is 40.. not possible..

Only when X>Y, the equation is satisfied..

Regards,
Viju
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PostTue Nov 10, 2009 8:04 am
viju9162 wrote:
answer is B. Reasoning is as follows:

From A, it states that y>4.

X+y=10..therefore if Y=5, X should be 5.. or if Y=6, X should be 4 ...From A, X can be equal to Y or can be less than Y..

Hence not sufficient..

From B, The cost of the 10 kilograms of material K is less than $40.

Therefore, 3X+5Y<40.. start inputting values for x and y..
Consider, X=3 and Y=7.. it crosses 40..not possible..

If X =5, Y=5, it is 40.. not possible..

Only when X>Y, the equation is satisfied..

Regards,
Viju
How about if x = 3 and y = 5 ? Doesn't it give an answer < 40 and x < y ?
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PostTue Nov 10, 2009 9:27 am
X+Y should equate to 10 Smile .. 5+3 is only 8 ..
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PostTue Nov 10, 2009 1:26 pm
FML Very Happy i DON'T KNOW HOW I TAKE THE GMAT Mad
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PostThu Jan 21, 2010 10:07 pm
well explained viju Very Happy
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