Answer:
The score of her next test is 96
Step-by-step explanation:
If there is a set of data with x terms, then the average is the sum of their values divided by x
Average = sum of values of the x terms ÷ x
We will use this rule to solve the question
∵ Marsha's scores on 7 test were 82, 78, 77, 93, 85, 91, 86
→ Find her total scores on the seven tests
∴ Her total scores = 82 + 78 + 77 + 93 + 85 + 91 + 86 = 592
∴ Her total scores on the 7 tests is 592
∵ Her average score on the 8 test is 86
→ Use the rule of the average to find her total score in the 8 test
∵ 86 = total scores ÷ 8
→ Multiply both sides by 8
∴ 86 × 8 = total scores × 8 ÷ 8
∴ 688 = total scores
∴ Her total scores on the 8 tests is 688
∵ Her total scores on the 7 test = 592
∵ Her total scores on the 8 test = 688
→ The difference between both totals is the score of her next test
∴ The score of her next test = 688 - 592 = 96
∴ The score of her next test is 96
