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# If wx = y, then what is the value of xy?

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Manager
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If wx = y, then what is the value of xy?  [#permalink]

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31 Dec 2010, 04:51
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65% (00:43) correct 35% (01:08) wrong based on 321 sessions

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If wx = y, then what is the value of xy?

(1) w*x^2 = 16
(2) y = 4
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Posts: 48097
Re: If wx = y, then what is the value of xy?  [#permalink]

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31 Dec 2010, 06:22
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jonblazon wrote:

if wx=y, then what is the value of xy?

1) wx^2= 16 (w times x squared)

2) y= 4

thanks!

If wx=y, then what is the value of xy?

(1) wx^2 = 16 --> $$x*(wx)=16$$ --> as given that $$wx=y$$ then $$x*y=16$$. Sufficient.

(2) y = 4 --> clearly insufficient: question becomes $$4x=?$$, and all we know is that $$wx=4$$.

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Manager
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Re: If wx = y, then what is the value of xy?  [#permalink]

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31 Dec 2010, 07:08
super thanks! should have seen it was that easy
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Re: If wx = y, then what is the value of xy?  [#permalink]

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01 Jan 2011, 08:45
+1 for Jonblazon for good question. I got C for uncareful observation
+1 for Bunuel: you are amazing
Thanks once again for your good question, at least to me.
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Re: If wx = y, then what is the value of xy?  [#permalink]

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05 Mar 2014, 09:45
Usually when I have a DS question I try to come up with the equations and respective variables that I need. Then I count the equations and unknowns and if I have more unknowns than I have equations I know it's not sufficient.
Here I'm not sure if the approach is feasible, but I'd like to give it a try. Please give me your opinions on the approach:

1. We have the equation wx = y and we need to find xy = ?. In order to do so we don't need to know x or y, but only w (if we have w, we're able to find xy, as wx = y is given). Therefor w is our only unknown.

(1) we get wx^2=16. As we don't need to handle x as an unknown (see above) we can count what we have: here it's 1 unknown (w) and 1 equation => sufficient
(2) we get y=4. y isn't an unknown in this approach, so when we count: 1 unknown (w) and 0 equations => not sufficient

So it's A.
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Re: If wx = y, then what is the value of xy?  [#permalink]

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28 Oct 2015, 21:27
1
i mistakenly took it as (wx)^2
and got wx = +-4 which is insufficient; 2 is as well insufficient..
eh..can't say it's not my fault, but the topic starter should have put the math code here :D
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Re: If wx = y, then what is the value of xy?  [#permalink]

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29 Oct 2015, 00:22
mvictor wrote:
i mistakenly took it as (wx)^2
and got wx = +-4 which is insufficient; 2 is as well insufficient..
eh..can't say it's not my fault, but the topic starter should have put the math code here :D

The point is that wx^2 mathematically can only mean w*x^2. If it were (wx)^2 it would be written that way. Still edited to avoid confusion.
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Re: If wx = y, then what is the value of xy?  [#permalink]

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29 Oct 2015, 06:55
Bunuel wrote:
mvictor wrote:
i mistakenly took it as (wx)^2
and got wx = +-4 which is insufficient; 2 is as well insufficient..
eh..can't say it's not my fault, but the topic starter should have put the math code here :D

The point is that wx^2 mathematically can only mean w*x^2. If it were (wx)^2 it would be written that way. Still edited to avoid confusion.

Thanks bunuel, but it was not needed. I admit that it was my mistake, and that I should have been more attentive. Indeed wx^2 represents w*x^2

I was speaking about $$wx^2$$ rewriting in this format
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Re: If wx = y, then what is the value of xy?  [#permalink]

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10 Dec 2017, 03:22
I'm sorry, I've spent 20 mins trying to puzzle this out but just can't get it.

What if we were to pick numbers?

WX=Y

If W were 1 and X were 4, then Y would be 4.

Using statement 1; WX^2 = 16 would mean 1 x 4^2 = 16

This satisfied the number I'd picked earlier and Y remains 4.

But if I had chosen W as 16 and X as 1, then WX = 16

Using statement one -> 16 x 1^2 = 16

This also satisfied picking W as 16 and X as 1, but now the value of WX is 16 wich means that Y is also 16.

So i get two different possible values for Y: 4 and 16.

What am I doing wrong?
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Re: If wx = y, then what is the value of xy?  [#permalink]

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10 Dec 2017, 04:09
calappa1234 wrote:
I'm sorry, I've spent 20 mins trying to puzzle this out but just can't get it.

What if we were to pick numbers?

WX=Y

If W were 1 and X were 4, then Y would be 4.

Using statement 1; WX^2 = 16 would mean 1 x 4^2 = 16

This satisfied the number I'd picked earlier and Y remains 4.

But if I had chosen W as 16 and X as 1, then WX = 16

Using statement one -> 16 x 1^2 = 16

This also satisfied picking W as 16 and X as 1, but now the value of WX is 16 wich means that Y is also 16.

So i get two different possible values for Y: 4 and 16.

What am I doing wrong?

What question are you answering? The question asks: what is the value of xy? In both of your examples xy comes to be 16.
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Re: If wx = y, then what is the value of xy?  [#permalink]

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10 Dec 2017, 10:25
Oh my, never mind! I've been trying to read way to deep into this question and have in turn, contorted it into something else entirely in my mind. I see now, how simple it actually is. Sorry for the confusion, and thanks for clearing it up!
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Re: If wx = y, then what is the value of xy?  [#permalink]

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22 Mar 2018, 21:31
If wx = y, then what is the value of xy?

(1) w*x^2 = 16
(2) y = 4

I solved it like this
1) w*x^2 /x^2 = 16/x^2 (divide by x^2 on both side)
w= 16/x^2
Put this in original equation wx = y --> (16/x^2)*x = y -->16/x = y
So, xy = x* (16/x) = 16 Hence, sufficient.

Can we solve it this way aswell??
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Re: If wx = y, then what is the value of xy?  [#permalink]

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22 Mar 2018, 22:15
RashmiT wrote:
If wx = y, then what is the value of xy?

(1) w*x^2 = 16
(2) y = 4

I solved it like this
1) w*x^2 /x^2 = 16/x^2 (divide by x^2 on both side)
w= 16/x^2
Put this in original equation wx = y --> (16/x^2)*x = y -->16/x = y
So, xy = x* (16/x) = 16 Hence, sufficient.

Can we solve it this way aswell??

Hello

Yes, I think we can do it this way as well.
Re: If wx = y, then what is the value of xy? &nbs [#permalink] 22 Mar 2018, 22:15
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