Final answer:
To get a quiz average of 70 or better, you need a minimum grade of 72 on quiz 5.
Step-by-step explanation:
To find the minimum grade needed on quiz 5 to get a quiz average of 70 or better, we can use the formula:
Minimum grade = (required average × total number of quizzes) - sum of grades on previous quizzes
Let's plug in the given values:
Total number of quizzes = 5
Required average = 70
Sum of grades on previous quizzes = 84 + 62 + 59 + 73 = 278
Now, let's calculate the minimum grade:
Minimum grade = (70 × 5) - 278
Minimum grade = 350 - 278
Minimum grade = 72
Therefore, the minimum grade needed on quiz 5 to get a quiz average of 70 or better is 72.