Algebra Demystified 2nd Ed

Chapter 8 linear appliCaTionS 253

Let x represent the project grade.

2

3

87 1

3

90

58

3

90

358

3

390

3583

()

()

()

+=

+=

 +







=

+

x

x

x

x

33

270

174 270

174 174

96









=

+=

−−

=

x

x

Allan needs a 96 on his project to raise his average to 90.

PRACTICE

1. Crystal’s grades are 93, 89, 96, and 98. What does the next grade have
   to be to raise her average to 95?


2. Nichelle’s grades are 79, 82, 77, 81, and 78. What does the next grade
   have to be to raise her average to 80?


3. A presentation grade counts toward one-fourth of the course grade. The
   average of the four tests counts toward the remaining three-fourths of
   the course grade. If a student’s test scores are 61, 63, 65, and 83, what does
   he need to make on the presentation grade to raise his average to 70?


4. The final exam accounts for one-third of the course grade. The average
   of the four tests accounts for another third, and a presentation accounts
   for the final third. Ava’s tests scores are 68, 73, 80, and 95. Her presenta-
   tion grade is 75. What does the final exam grade need to be to raise her
   average to 80?


5. A book report counts toward one-fifth of a student’s course grade. The
   remaining four-fifths of the courses’ average is determined by the aver-
   age of six quizzes. One student’s book report grade is 90 and has quiz
   grades of 72, 66, 69, 80, and 85. What does she need to earn on her sixth
   quiz to raise her average to 80?

PRACTICE

1. Crystal’s grades are 93, 89, 96, and 98. What does the next grade have