Practice question #1: D
Explanation: If the starting salaries were 0 (or anything close to 0),
then the $10,000 difference between raises in year 2 would dwarf the
10% difference in year 1, and A would end up with a higher salary.
But if the starting salaries were high (a million dollars, say), 
then the 10% difference in year 1 would dwarf the $10,000 difference
in year 2, and B would end up with a higher salary.

Practice question #2: B
Explanation: We need to solve the ratio
X miles / 6 inches = 700,000 calories / 250 calories.
Write this as
(5280X feet) / (.5 feet) = 700,000 calories / 250 calories,
or 5280X / .5 = 700,000 / 250.  Solving, we get
X = (700,000 / 250) (.5 / 5280) = .265, which is about 1/4.

Practice question #3: D
The population increased by 11.4 million minus 9 million,
or 2.4 million.  This represents a proportional increase of
2.4 million / 9 million, or 0.2667, or 26.67%.  However,
the denominator (9 million) has only one significant digit,
so the 2.4 / 9 has only one significant digit, and we must
round 26.67% to 30%.
Recall that one is not supposed to round intermediate steps.
If you rounded 2.4 million down to 2 million before dividing
by 9, you would get 0.2222, and then rounding again (using
one significant digit), you would get 20%, which is not as
good an approximation to the true answer as 30%.

Practice question #4: D
Explanation: $400 / $20 = 20 = 2000%.

Practice question #5: B
Explanation: Assume a population of 10,000 men.  Of these
men, 5% (= 500) have prostate cancer and the rest (= 9500) don't.  
Of the 500 who have prostate cancer, 95% (= 475) will test positive 
the rest (25) will test negative.  Of the 9500 who don't have prostate
cancer, 90% (= 8550) will test negative, and the rest (950) will
test positive.  Thus, out of the 475+950 = 1425 men who test positive,
only 475 actually have prostate cancer.  475/1425 = .33 = 33%.

Practice question #6: C
Explanation: When you put your money in the Cassidy bank for a
year, it gets multiplied by 1.12; when you put your money in
the Dillinger bank for a year, it gets multiplied by (1.03)^4.
So, if you put your money in each bank for a year, at the
end of two years it will have been multiplied by 1.12 x (1.03)^4,
under both scenarios.

Practice question #7: D
Explanation:
By the Savings Plan Formula (with A = $1000, APR = 12%, n = 12,
and Y = 1/4, you must deposit
$1000 x (0.01)/(1.01^3-1) = $330 per month.

Practice question #8: B
Explanation: If we plug into the Loan Payment Formula
(P = unspecified, APR = 0.12 for Frankie and 0.06 for Johnny,
n = 12, and Y = 15 for Franie and 30 for Johnny), we see that
Frankie's monthly payment equals P times
(0.12/12)/[1-(1+0.12/12)^(-12*15)], or P times 0.012,
while Johnny's monthly payment equals P times
(0.06/12)/[1-(1+0.06/12)^(-12*30)], or P times 0.006.