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Question 2 (nov.24th)

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Question 2 (nov.24th)

by bacali » Mon Nov 24, 2008 11:37 am
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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by cramya » Mon Nov 24, 2008 1:09 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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by uptowngirl92 » Mon Oct 19, 2009 11:58 pm
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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by Abdulla » Fri Nov 06, 2009 10:35 pm
yeah uptowngirl92, this is the same question that came to my mind.

We need explanation pls..
Abdulla
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by life is a test » Sat Nov 07, 2009 3:06 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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Re: Question 2 (nov.24th)

by palvarez » Sat Nov 07, 2009 7:26 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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by heshamelaziry » Mon Nov 09, 2009 4:00 pm
I understand the algebra solution by cramya. But if I try numbers, x can be less than or more than y.

:(
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by viju9162 » Mon Nov 09, 2009 9:52 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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by heshamelaziry » Tue Nov 10, 2009 7:04 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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by viju9162 » Tue Nov 10, 2009 8:27 am
X+Y should equate to 10 :) .. 5+3 is only 8 ..
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by heshamelaziry » Tue Nov 10, 2009 12:26 pm
FML :D i DON'T KNOW HOW I TAKE THE GMAT :x
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by bhumika.k.shah » Thu Jan 21, 2010 9:07 pm
well explained viju :D
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by skprocks » Sat Jul 10, 2010 8:52 pm
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
The point is that the Q asks if x>y?
From Stmt 1: y>4 so Is x>y will have answer No,when y>4 (Case : X=5,Y=5, still X>y has the answer No.)
and in all other cases for Y>5 X>y has answer No.Not a single case exists where X>Y.
If Y>4

From Stmt2: Explannation is clear.

Hence,Why can't the answer be D.
Is X=Y not indicating that,X> Y is False.
When Y>4, still X>Y is False/No.
Please throw some light.

Sorry,for my misinterpretation just looked up OG12 soln and found that for Statement 1: a scenario arises like x=5.5 and y=4.5.meaning that x>y has an answer Yes.And when y=5,x=5 indicates that X>Y has an answer No.
So,Statement 1 is insufficient.
Key take away is that x and y are not integers.
Last edited by skprocks on Sat Jul 10, 2010 9:05 pm, edited 1 time in total.
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by diebeatsthegmat » Sat Jul 10, 2010 9:03 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.


OA: B
hmhm
i would love to solve this problem by this way
x+y=10
from statement 2. we know that
3x+5y<40
thus we have
x=10-y and 3x+5y<40
we solved all those above and we have the result of y<5 =4,5,2,1 and x could be 6,7,8,9
from these results we know that x is always larger/bigger than y
thus statement II is sufficient
statement I
from statement II we solved
we take x=5and y=5 >>> 5+5=10
x=3 y=7 >>> #+7=10
thus statement I is not insufficient
OA is B
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