Cracking The SAT Premium

increased   by  27  –   15  =   12. The correct answer  is  (C).

6. B This   is  a   good    Plug    In  the Answers problem.    Start   with    (B) and plug    in  2   for x   and 3   for r   in

the equation    to  get V   =   24π +   2 , which   is  equal   to  the target  amount  of  96π,    so  (B)

is  correct.

7. C Whenever   there   are variables   in  the question    and in  the answers,    think   Plugging    In. Let c   =

30. Therefore, b = 2 + (30) = 2 + 10 = 12. Plug 12 in for b in the answers to see which

answer  equals  the target  number  of  30. Choice  (A) becomes  .  Eliminate

(A),    since   it  does    not equal   the target  number. Choice  (B) becomes .

Eliminate   (B).    Choice  (C) becomes 3(12    –   2)  =   3(10)   =   30. Keep    (C),    but check   (D) just    in

case    it  also    works.  Choice  (D) becomes 3(12    –   6)  =   3(6)    =   18. Eliminate   (D).    The correct

answer  is  (C).

8. D Treat   this    question    as  a   translation     problem.    According   to  the     question,  R(h)     =   four

rotations   per second  less    than    three   times   the square  of  the height  of  the liquid. The height  of

the liquid  is  represented by  h.  Therefore,  three   times   the square  of  the height  of  the liquid  =

3 h^2 . Four    less    than    this    amount  is  3h^2    –   4.  Since   the original    speed   was 1,000,  subtract    this

value   from    1,000   to  get the current rate    of  rotation.   The correct answer  is  (D).

9. B Start  with    the easier  equation    and use Process of  Elimination.    The easier  equation    is  related

to  the total   number  of  ounces, c   +   b,  in  the tube.   According   to  the question,   the tube    has 24

ounces, so  c   +   b   =   24. Eliminate   (A),    since   it  does    not include this    equation.   The other

equation    in  the set is  related to  the amount  of  active  ingredients.    According   to  the question,

c   includes    0.25%   of  sodium  fluoride    and b   contains    0.30%   triclosan.  0.25%   =   0.0025  and

0.30%   =   0.003.  Therefore,  in  the correct equation,   c   should  be  associated  with    0.0025  and

b   should  be  associated  with    0.003.  Eliminate   (C) and (D) because both    of  these   equations

get the percentages wrong.  The correct answer  is  (B).

10. C Whenever the question includes variables and the answer choices are numbers, think

Plugging     In  the     Answers.    In  (A),    d   =   –4,     and     the     equation    becomes    

. Solve both sides of the equation to get

,   or   .  Reduce  both    fractions   to  get –13 =   –5. This