Please help on these DS questions!

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Please help on these DS questions!

by srinivasapriyan.r » Sun Nov 03, 2013 11:40 pm
Choice highlighted with box is OA.

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by mevicks » Mon Nov 04, 2013 1:58 am
Firstly, please post a single question per thread to avoid confusion.

Now, coming back to the original question:

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In the figure shown, what is the value of x ?
(1) The length of line segment QR is equal to the length of line segment RS.
(2) The length of line segment ST is equal to the length of line segment TU.
Q: x = ?

St1:

QR = RS
This is not at all helpful and in no way helps to find x (cant use similar triangles property, etc)
INSUFFICIENT

St2:
ST = TU
This is not at all helpful and in no way helps to find x (cant use similar triangles property, etc)
INSUFFICIENT

St1+St2:
Image
In the bigger right angled ∆RPT the sum of the angles R + T = 180 - 90 = 90
But In the isosceles ∆RQS, R + a + a = 180 ; R + 2a = 180 ; R = 180 - 2a
Similarly, In the isosceles ∆STU, T + b+ b = 180 ; T + 2b = 180 ; T = 180 - 2b

Thus, 180 - 2a + 180 - 2b = 90
We can find a + b.
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Now a + x + b = 180 and thus we can find x

SUFFICIENT

Answer C

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by mevicks » Mon Nov 04, 2013 2:11 am
Second question is already discussed here: www.beatthegmat.com/distance-between-x- ... 71155.html
On the number line, the distance between x and y is greater than the distance between x and z. Does z lie between x and y on the number line?
(1) xyz<0
(2) xy< 0
Given: Distance between x&y is GREATER than the distance between x&z, ie. on a number line xy is a bigger line segment and xz is a smaller one.

Image

Q: We need to find out whether z lies between x and y or not

St1:
xyz < 0
product is negative so either all could be -ive or two could be -ive and one could be +ive

There could be many possibilities with these combinations and z MAY or MAY not lie inside:
Image

INSUFFICIENT
(All the possibilities need not be visualized here only a few should suffice)

St2:
xy< 0
Either x = +ive & y = -ive
or x = -ive & y = +ive
We know nothing about Z and z could lie inside or outside.
INSUFFICIENT

St1+St2:
Combining the two inequalities we know that Z is +ive

Case1 (x = +ive & y = -ive & Z = +ive) :
Image

Case2 (x = -ive & y = +ive & Z = +ive):
Image

More than one possibility, thus INSUFFICIENT

[spoiler]Answer : E[/spoiler]

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by mevicks » Mon Nov 04, 2013 2:16 am