In terms of...

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Kemmy G: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Wed Apr 06, 2011 8:50 amFollowed by: 1 member

by Kemmy G » Tue Aug 09, 2011 8:47 am

Hi.

I've been studying the quant. topics for a while now, but I find I keep getting thrown off course by questions that state- if x is half of y, and y is three-quarters of z, what is x in terms of z???.

Can someone please explain what that phrase means- what is 'x' in terms of 'y'. I don't clearly get it, so I have problems solving the question. I'll really appreciate clear answers or explanations. Thanks.

Kemmy

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Source: Beat The GMAT — Quantitative Reasoning | Tue Aug 09, 2011 8:47 am

Touseef: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Sat Jul 30, 2011 10:39 pm; Location: India; Thanked: 3 times

by Touseef » Tue Aug 09, 2011 9:13 am

Hi Kemmy,

This is a simple logic

lets say,X=5 and Y=10.So you can say that

X=1/2Y(Since X=1/2(10)=5
or Y=2X(Since,Y=2*5=10)

A more simpler example,U hav 2 apples and I have 4 apples,So u have half as much apples as I have.4(My apples)*1/2=2(ur apples).

I have twice as much Apples as you have.2(Ur apples)*2=4(my apples).

So,
when X=1/2Y i.e Y=2X
Y=3/4Z

Hence,2X=3/4Z or X=3/8Z(The Ans)

Hope this helps

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Kemmy G: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Wed Apr 06, 2011 8:50 amFollowed by: 1 member

by Kemmy G » Mon Aug 15, 2011 12:56 am

Hi Touseef.

Thank you for replying,

! I read your explanation again and again, and it still wasn't very clear, so I went back and hit the books. I think I understand it a bit better now, but any other concise, perhaps very basic explanation is still welcome. Thanks again.

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Tani: Legendary Member; Posts: 1255; Joined: Fri Nov 07, 2008 2:08 pmFollowed by: 90 members; Location: St. Louis; Thanked: 312 times

by Tani » Tue Aug 16, 2011 8:13 am

"X in terms of Z" simply means you are asked to get X on the left side of the equation and all constants plus any terms including Z (and no other variables) on the right side. When you start with X, Y and Z, you have to find a way to eliminate Y entirely. That usually means getting Y in terms of Z and then plugging back into the original equation.

In this example:

x = y/2
y = (3z)/4

Substituting the expression for Y in the second equation [(3z)/4] back into the first equation we get:

x = [(3z)/4]/2 = (3Z)/8

If the algebra makes it difficult for you try picking numbers.

Let y = 12 (you want a number divisible by both 2 and 3 so you don't have to deal with fractions)

Then x = 6 and z = 16

Plugging these back into our answer we get 6 = (3*16)/8 which is 48/8 = 6. Correct!

Tani Wolff

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