GRE-Math-Questions-to-Know-by-Test-Day-2nd-Edition_pag196

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Answers ‹ 187
176. 500 Let x = the number of balcony seats sold, and y = the number of orchestra seats 
sold. Write and solve simultaneously the following two equations:
 (1) + =x y 800 
 (2) + =x y$50 $80 $49,000 
 Solve (1) for y and substitute into (2). Omit units and solve for x.
 ( )+ − =x x50 80 800 49,000 
 + − =x x50 64,000 80 49,000 
 − = −x30 15,000 
 =x 500 
177. 
1
6
 Let w = the number of white marbles in the box, b = 2w = the number of black 
marbles in the box, and r = + = =b b b w50% 1.5 1.5(2 ) = 3w = the number of red marbles 
in the box. Then the probability, P, of randomly drawing a white marble from the box is:
P = 
+ +
w
w b r
 = 
+ +
w
w w w2 3
 = =w
w6
1
6
 
178. −−1133 Let n = the lesser integer, and +n 1 = the greater integer. Write and solve the 
following equation:
 + =n n( 1) 182 
 + − =n n 182 02 
 + − =n n( 14)( 13) 0 
 Thus, n is −14 with + = −n 1 13 or n = 13 (reject).
179. 300 + = − −x xy y xy1002 2 , which can be rewritten as follows:
+ + =x xy y2 1002 2 
 + =x y( ) 1002 
Thus, + = + = + = =x y x y x y( 3 3) ( 3) ( ) 3( ) 3(100) 3002 2 2 2 .
180. 0.125
=a 25 ⇒ =a 25 ⇒ = = = = =− − −a (2 ) 2 1
2
1
8
0.1250.6 5 0.6 3
3
. Note: ⇒ means “implies.”
06_McCune_Answer.indd 187 2/21/22 4:47 PM