12.Practice.Tests.for.the.SAT_2015-2016_1128p

12 Practice Tests for the SAT
Practice Test Nine Answers and Explanations
833
I
5. c
Difficulty: Medium
Strategic Advice: This question involves solving an algebraic
equation and working with decimals, so if you had trouble
with it, you might need to review one or both of those
topics. All you have to do to solve this problem is work with
the equation step-by-step until you get x alone on one side:
Getting to the Answer:
0.4x + 2 = 5.6 Subtract 2 from both sides.
6. B
0.4x = 3.6 Multiply both sides by 10 to get rid of
the decimals.
4x =36
X=9
Difficulty: Medium
Divide by 4.
And you've found x, (C).
Strategic Advice: If a rectangle has a perimeter of 12, then
2(W + L) = 12, where Wis the width of the rectangle and L
is its length.
Getting to the Answer:
If 2(W + L) = 12, then W + L = 6. If the width is 2 less than
the length, then W = L - 2. You can plug L - 2 for W into
the equation W + L = 6, so W + L = 6 becomes (L - 2) +
L = 6 and so 2L - 2 = 6, 2L = 8, and L = 4. If the length is
4, then the width, which is 2 less, must be 2. The area of a
rectangle with length 4 and width 2 is 4 x 2 = 8, (B).
7. c
Difficulty: Medium
Strategic Advice: The easiest way to do this one is to just
draw lines from each point and then add up the number of
line segments drawn.
Getting to the Answer:
From point A, draw one line to each of points 8, C, 0, and
E. From point 8, you already have a line to point A, so just
draw a line to each of points C, 0, and E. From point C, you
have already drawn lines to A and 8, so draw in a line to
point 0 and one to point E. Finally, draw a line from point
0 to point E. (You've drawn a star inside a pentagon-very
artistic!) Can you see any point that is unconnected to any
other point? No, so just add up the number of lines you've
already drawn-there are 4 + 3 + 2 + for 10 of them, (C).
8. B
Difficulty: High
Strategic Advice: Whenever you have a percent word
problem that doesn't give you a definite amount and asks
you a question like What fraction of the total . .. ?, you
should pick a number for the total.
Getting to the Answer:
Since you're dealing with percents here and will be
converting the percents to fractions, a good number for
the total is 100. So, say that 100 people were polled:
80 percent of the 1 00 people were registered voters, so 80
people were registered voters; 75 percent of the registered
voters voted in the last election, so 750/o x 80, or 60 people
voted in the last election. If 60 of the 80 registered voters
actually voted in the last election, then 80 - 60 = 20 of the
registered voters didn't vote in the last election. The fraction
of the people surveyed who were registered but didn't vote
. 20 1
IS ( )
100' or s. , B.
9. E
Difficulty: High
Strategic Advice: Mixture problems are very tricky. The
important thing to look for in a mixture problem is this:
Which quantities stay the same, and which quantities
change? Here, the alcohol is evaporating but the iodine is
not. Therefore, the quantity of iodine will be unchanged.
Getting to the Answer:
So, start with 4 ounces of iodine and 1 6 ounces of alcohol
and end with 4 ounces of iodine and an unknown quantity
of alcohol, which you can call x ounces. That means that
in the end, the whole solution has a total of 4 + x ounces,
since the solution is made up of only iodine and alcohol.
The final quantities of iodine and total solution are in the
ratio of 2 to 3. That means that the ratio of 4 to 4 + x is
equal to the ratio of 2 to 3, or 4
! x
= 1-. which is just an
algebraic equation that can be easily solved:
4 2
4+x - 3
Cross-multiply.
2( 4 + x) = 4 x 3 Multiply out the left side.
8+2x= 12 Subtract 8.
2x =4 Divide both sides by 2.
x=2 That's the amount of alcohol left.