ANSwER ExPlANATIONS
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SAT Practice Test #8
QUESTION 25
Choice A is correct. It is given that the relationship between
population and year is linear; therefore,
the function that models
the population
t years after 2000 is of the form
P (
t) =
mt +
b,
where
m is the slope and
b is
the population when t = 0.
In the year 2000,
t = 0. Therefore,
b = 862. The slope is given by
m =
P(10) −
P(0)
__
10 − 0 =
846 − 862
_
10 − 0 =
−16
_
10 = −1.6. Therefore,
P (
t) = −1.6
t + 862,
which is equivalent to the equation in choice A.
Choice B is incorrect and may be the result of incorrectly calculating
the slope as just
the change in the value of P. Choice C is incorrect
and may be the result of the same error as in choice B, in addition to
incorrectly using
t to
represent the year, instead of the number of years
after 2000. Choice D is incorrect and may be the result of incorrectly
using
t to represent the year instead of the number of years after 2000.
QUESTION 26
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