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Math B Regents Exam Questions by Type - 4 Point Free Response Page 14
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79. The cost (C) of selling x calculators in a store
is modeled by the equation
3, 200,
000
C = + 60 , 000 . The store profit (P)
x
for these sales is modeled by the equation
P = 500 x. What is the minimum number of
calculators that have to be sold for profit to be
greater than cost?
81. The height of a projectile is modeled by the
2
equation y =− 2x + 38x+
10, where x is
time, in seconds, and y is height, in feet.
During what interval of time, to the nearest
tenth of a second, is the projectile at least 125
feet above ground? [The use of the
accompanying grid is optional.]
80. In a mathematics class of ten students, the
teacher wanted to determine how a homework
grade influenced a student's performance on
the subsequent test. The homework grade and
subsequent test grade for each student are
given in the accompanying table.
82. On any given day, the probability that the
entire Watson family eats dinner together is
2
. Find the probability that, during any 7-
5
day period, the Watsons eat dinner together at
least six times.
a Give the equation of the linear regression
line for this set of data.
b A new student comes to the class and earns
a homework grade of 78. Based on the
equation in part a, what grade would the
teacher predict the student would receive on
the subsequent test, to the nearest integer?
83. Two equal forces act on a body at an angle of
80°. If the resultant force is 100 newtons,
find the value of one of the two equal forces,
to the nearest hundredth of a newton.
84. The amount A, in milligrams, of a 10-
milligram dose of a drug remaining in the
body after t hours is given by the formula
t
A = 10(.). 08 Find, to the nearest tenth of an
hour, how long it takes for half of the drug
dose to be left in the body.