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#