Jane has scored the following marks on the first $5$ exams: $65, 70, 55, 87, 87.$ What is the minimum score she must achieve on the last exam if she is to reach her target of a $70%$ average?

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Answer 1 · 2017-09-20T04:07:14

$61$

$"Sum of the scores of 5 exams" = 65+70+55+82+87 = 359$

$"Average of 6 exams" = ("sum of 5 exams" + x) / 6$

where $x$ is the min. score required in exam $6$ .

$70 = ( 359 + x ) / 6$

$6 * 70 = 359 + x$

$420 = 359 + x$

$x = 420 - 359$

$x = 61$

So $61$ is the min mark required in exam $6$ for a final grade of C.

Answer 2 · 2017-09-20T11:43:39

She needs at least $61$ in the sixth exam.

$"Mean" = "Total"/"Number"$

From this we can calculate the $"Total"$ by multiplying:

$"Total" ="Mean"xx"Number"$

If the average for $6$ exams must be $70$ , the total for all $6$ exams must be:

$T = 6xx70 = 420$

Jane's total after $5$ exams is: $60+70+55+82+87 = 359$

Therefore in the last exam she should score a mark of at least:

$420-359=61$

$(60+70+55+82+87+61)/6=70$

Jane has scored the following marks on the first 55 exams: 65, 70, 55, 87, 87.65, 70, 55, 87, 87. What is the minimum score she must achieve on the last exam if she is to reach her target of a 70%70% average?