GRE Exam Numerical Ability Number System

Question
If the integer a is a multiple of 6, the integer b is a multiple of 3, and a>b>0, then which of the following integers must be a^2 – b^2 multiple of?
A. 6
B. 8
C. 9
D. 10
E. 12

Read Solution (Total 1)

let a=6x;
b=3y;
a^2-b^2=36x^2-9y^2
=9(4x^2-y^2)
hence answer is 9
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GRE Other Question

Question
1. It is refreshing to read a book about our planet by an author who does not allow facts to be (i)__________ by politics: well aware of the political disputes about the effects of human activities on climate and biodiversity, this author does not permit them to (ii)__________ his comprehensive description of what we know about our biosphere. He emphasizes the enormous gaps in our knowledge, the sparseness of our observations, and the (iii)__________, calling attention to the many aspects of planetary evolution that must be better understood before we can accurately diagnose the condition of our planet.
Blank (i)
(a) overshadowed
(b) invalidated
(c) illuminated
Blank (ii)
(d) enhance
(e) obscure
(f)underscore
Blank (iii)
(g) plausibility of our hypotheses
(h) certainty of our entitlement
(i) superfi ciality of our theories Question
If a sweater sells for $48 after a 25 percent markdown, what was its original price?
A. $56
B. $60
C. $64
D. $68
E. $72