Exam question #1: A
Explanation: Employee A's salary first gets multiplied by 1.20 and
then gets multiplied by 0.90, so she winds up with 1.20 x 0.90 = 1.08
times her original salary.  Employee B's salary first gets multiplied 
by 1.30 and then gets multiplied by 0.80, so she winds up with 
1.30 x 0.80 = 1.04 times her original salary.  Since 1.08 > 1.04,
employee A's salary is higher.

Exam question #2: C
Explanation: X is to 170 as 1.3 billion is to 6.6 billion, 
so X = 170 * (1.3 billion / 6.6 billion) = 33.48, 
which is closer to 30 than to any of the other choices.
If you don't have a calculator, there are various ways
to estimate this accurately.  For instance, to estimate
1.3 billion / 6.6 billion, write it as 13 / 66; since
66 is close to a multiple of 13 (namely 65), 13 / 66
can be approximated by 1 / 5, and 170 * (1 / 5) = 34.
If this seems too close to 35 for comfort (how do we 
know that the true answer isn't 36, which would be
closer to 40 than to 30?), notice that since 66 is 
greater than 65, 13 / 66 is less than 13 / 65 = 1/5, 
so 170 * (13 / 66) is less than 34.

Exam question #3: C
Explanation: 11.11 is accurate to within a hundredth of an inch,
but 1.1 is accurate only to within a tenth of an inch, so the
sum 12.21 is only accurate to within a tenth of an inch; that
is, the length plus the width is 12.2 inches, so the perimeter
is 24.4 inches.  As for area, 11.11 has four significant digits,
but 1.1 has only two, so the product 12.221 is only accurate to
two significant digits, and the area is 12 square inches.
Note that the "2" that we multiply when computing perimeter
is a mathematical constant, not a measured quantity, so the
rules about rounding do not apply to it; in particular, we do
not say "since 2 has only one significant digit, the perimeter
has only one significant digit".  (If this were true, then
NO rectangle would ever have more than one significant digit
in its perimeter!)  See page 177, "Combining Measured Numbers".

Exam question #4: C
Explanation: The CPI in 1987 was 113.6, and the CPI
in 1997 was 160.5.  So anything that cost $98.38 in 1987 
would be expected to cost $98.38 times (160.5/113.6) = $139
in 1997.  $139 is closer to $140 than to any of the other
choices.

Exam question #5: C
Explanation: Out of 100 students, 10 use drugs and 90 don't.
Of the 10 drug users, 9 will test positive; of the 90 non-users,
9 will test positive.  Of the 18 students who test positive,
only 9 are drug-users; the other 9 (representing half, or
50%, of the students who tested positive) are falsely accused.

Exam question #6: C
Explanation: When money is invested at 20% compounded twice-yearly,
it gets multiplied by (1+.20/2)^2 = (1.1)^2 = 1.21, which is the
same as 21% compounded yearly.  So both grow equally quickly.

Exam question #7: C
Explanation: 
An APR of 12% compounded monthly means 12%/12, or 1%, each month.
On Feb. 28, you have $10,000+(1% x $10,000)+$10,000 = $20,100 in the bank.
On Mar. 31, you have $20,100+(1% x $20,100)+$10,000 = $30,301 in the bank.
Or, you can use the Savings Plan Formula with PMT = $10,000, APR = 0.12,
n = 12, and Y = 1/4 (since Mar. 31 is the end of the third month, and
three months is 1/4 of a year):
A = $10,000 x [(1+0.12/12)^(12/4)-1]/(0.12/12) = $30,301.

Exam question #8: B
Explanation: Moe's charges closing costs of $2000+$1000, while
Sam's charges closing costs of $1000+$2000, which is the same.
Hence the only difference comes from the interest rate.  Since 
Sam's is offering a lower interest rate, it's a better deal.
(No need to do interest calculations!)