Algebra Demystified 2nd Ed

254 algebra De mystif ieD

✔SOLUTIONS

1. Let x = the next grade.

93 89 96 98

5

95

376

5

95

5376

5

595

37

++++=

+ =

 +







=

x

x

x ()

66 475

376 376

99

+=

−−

=

x

x

Crystal’s last grade needs to be 99 in order to raise her average to 95.

2. Let x = the next grade.
   79 82 77 81 78
   6

80

397

6

80

6397

6

680

+++++ =

+ =

 +







=

x

x

x ())

397 480

397 397

83

+=

−−

=

x

x

Nichelle’s next grade needs to be 83 to raise her average to 80.

3. Let x represent the presentation grade. The test average is (61 + 63 + 65 +
   83)/4 = 68. Then^34 test average +^14 presentation grade = 70 becomes
   3
   468

1

()  +  4 x 70 = 

.

3

4

68 1

4

70

51

4

70

51 51

4

19

419

76

()

()

+=

+=

−−

=

=

=

x

x

x

x

x

The student needs a 76 on his presentation to have a course grade of 70.