Answers:
Work backwards.
In order to get an average score of 80 from four tests. when you add them all up, you must get the value of 320.
If you scores are 77 + 77 + 77 + ? = 320, You would need an 89. That way when you add them up, and divide by your number of tests (4) you get your 80
83
He needs an 89.
80 average for four tests = 320
He has a 77 avg now on 3 tests (77 x 3 = 231)
so 320-231=89
87
83
89
okay i gonna consider that the test is out of 100 points. so far you have 231 points. you have total 400 points. in order to get a B you need 320 points. hence you need to get a 89 on the fourth test to get a B
80x4=320 Thats the total needed
77+77+77 = 231
320-231=89 (answer)
83
89 for sure
87 will give you an 79.5 and 89 will give you exactly 80.
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