Question

Ty recieved test grades of 74%, 76%, 76%, 74%, and 82%. What grade would he need to make on the sixth test to get a C if a C is at least 75% but less than 80% ? is it possible for Ty to get an A for his test average (at least 90%)?

Answer 1

average of six tests = ( x1 + x2 + x3 + x4 + x5 + x6 ) / 6 =

In this case:

( 74 + 76 + 76 + 74 + 82 + x6 ) / 6 = ( 382 + x6 ) / 6


To get a C:

75 < ( 382 + x6 ) / 6 ≤ 80

1.

75 < ( 382 + x6 ) / 6

Multiply both sides by 6

450 < 382 + x6

Subtract 382 to both sides

68 < x6

x6 > 68

2.

( 382 + x6 ) / 6 ≤ 80

Multiply both sides by 6

382 + x6 ≤ 480

Subtract 382 to both sides

x6 ≤ 98

To get a C Ty need to score 68% to 98% points.


To get a A:

( 382 + x6 ) / 6 ≥ 90

Multiply both sides by 6

382 + x6 ≥ 540

Subtract 382 to both sides

x6 ≥ 158

Ty´s score on the test can't be ≥ 158%

Isn't possible to get an A.