Sat practice Test #8 Answer Explanations

The correct answer is 0. Note that no matter where point W is 
on
_
RT , the sum of the measures of 
∠RSW and ∠WST is equal to 
the measure of 
∠RST, which is 90°. Thus, ∠RSW and ∠WST are 
complementary angles. Since the cosine of an angle is equal to the 
sine of its complementary angle, cos(
∠RSW) = sin(∠WST). Therefore, 
cos(
∠RSW) − sin(∠WST) = 0.
QUESTION 37
The correct answer is 576. According to the table, 5 minutes after the 
injection, the penicillin in the patient’s bloodstream is 152 micrograms 
per milliliter. Thus, there are 10 × 152 = 1520 micrograms of penicillin 
in 10 milliliters of blood drawn 5 minutes after the injection. Similarly, 
10 minutes after the injection, the penicillin concentration is 
118 micrograms per milliliter. Thus, there are 8 × 118 = 944 micrograms 
of penicillin in 8 milliliters of blood drawn 10 minutes after the 
injection. Therefore, there are 1520 − 944 = 576 more micrograms of 
penicillin in 10 milliliters of blood drawn 5 minutes after the injection 
than in 8 milliliters of blood drawn 10 minutes after the injection.

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ANSwER ExPlANATIONS
| SAT Practice Test #8
QUESTION 38
The correct answer is 0.8. The value of b in the equation P (t) = 200b 
t 
_ 
5
can be estimated using any row of the table other than the first one. 
Substituting t = 5 and P (5) = 152 from the second row of the table 
into the definition of P yields 152 = 200b 
5 
_ 
5
, or 152 = 200b. Dividing 
both sides of this equation by 200 yields b = 152 
_ 
200 . The fraction can be 
rewritten as 76 
_ 
100 , or its decimal equivalent .76. Rounded to the nearest 
tenth, this value is .8. Other rows of the table also give a value of b that 
rounds to .8. Therefore, the value of b, rounded to the nearest tenth,
is .8. Either .8, or its fractional equivalents, 4/5 or 8/10, can be gridded 
as the correct answer.