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PS (Must be True) Explanation

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PS (Must be True) Explanation

by sabal » Sun Nov 16, 2008 12:03 am
Can someone please explain the answer to me.
I thought the answer should be E. However the answer is B.


If it is true that x>-2 and x<7, which of the following must be true?
A. x>2
B. x>-7
C. x<2
D.-7<x<2
E. None of the above
The answer is B

Any Explanations..
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by vishubn » Sun Nov 16, 2008 12:27 am
the key word here is "MUST " soooo no matter wat it has to be true !!

So we can plugin numbers ! but here the range is small ! can be derived !

first step is to see the condtion given and also when the equation is multiplied by -1 thru out

x>-2 and x<7[given]
x<2 and x>-7

A) Ruled out
B) is the answer ( coz if x > -7 so it also satisfies the cond x>-2)

C) x<2 ( tempting.. but the first condtion says x<7 sooo this dont qualify for "MUST" this qualifies for can be true
D) same here !!
E)not an option


Key to this kidna problem is ! the word MUST/Can be

Vishu
KILL !! DIE !! or BEAT my FEAR !!! de@D END!!
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by EricLien9122 » Sun Nov 16, 2008 12:38 am
In must be true questions, try to disprove the answer choice.

A. x>2, if x=-1, then x is not greater than 2.
B. x>-7, smallest x=-1.999 or largest x=6.9999, which both are greater than -7.
C. x<2, if x=6, then x is not less than 2.
D.-7<x<2, if x=5, then x is not in that range.


I hope this help, please correct me if I made a mistake
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by stop@800 » Sun Nov 16, 2008 2:11 am
x>-2 and x<7
means x lies between -2 and 7 [not inclusive]

Not lets look at each and every option...

x>2
what about the values less than 2
they are not covered.... x is from -2 to 7
so values between -2 and 2 are missed


x>-7
yes all values are covered, hence the answer.


x<2
what about values >2
x if from -2 to 7
here values from 2 to 7 are left out....

D
x lies between -7 and 2
but our x is -2 and 7
so incorrect

hence ans is B
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