a student has made scores f 83, 72, and 78 on three quizzes. what is the least score the student must make on a fourth quiz to ensure an average of 80?
2007-06-10 06:11:52 · 20 answers · asked by ashley t 2 in Science & Mathematics ➔ Mathematics
Recall that the average is the sum of the things you have, divided by how many there are.
80 = (83 + 72 + 78 +x)/4
320 = 83 + 72 + 78 + x
87 = x
Therefore, the person must get atleast 87% to have an 80% average
2007-06-10 06:17:01 · answer #1 · answered by Anonymous · 0⤊ 0⤋
83+72+78=233
since the average need to be 80 and there are 4 of them times 80 by 4. that comes to 320
then do 320-233 and that comes to 87
then add 83+72+78+87=320
now divide 320 by four and you get 80 as your average.
that means that you must score an 87 on the next quiz to ensure an average of 80.
2007-06-10 06:23:33 · answer #2 · answered by Rocketman 6 · 0⤊ 0⤋
An easy way would be to total the three scores and subtract from 320 which will be score for an average of 80 in four tests.
83 + 72 + 78 = 233
Subtracting that from 320 we get 320 - 233 = 87 as the minimum score needed in the 4th quiz.
Another way would be to subtract 80 from each score and sum them and find that number which is needed to make it 0.
Thus 83 - 80 = 3; 72 - 80 = - 8; 78 - 80 = -2
3 - 8 - 2 = -7 and so we need + 7 to make it 0. Thus adding +7 to 80, we get 87 as the answer.
2007-06-10 06:19:37 · answer #3 · answered by Swamy 7 · 0⤊ 0⤋
4 x 80 = 320
83+72+78 = 233
320 - 233 = 87 is needed for an average of 80
2007-06-10 06:20:43 · answer #4 · answered by Woody 3 · 0⤊ 0⤋
(83+72+78+x)/4 = 80
(83+72+78+x) = 80 * 4
(83+72+78+x) = 320
x + 233 = 320
x = 320-233
x = 87
2007-06-10 06:18:30 · answer #5 · answered by Sam 2 · 0⤊ 0⤋
83+72+78+x)/4 = 80 average of four scores
83+72+78+x = 80*4 means and extremes
83+72+78 +x = 320
x=320-83-72-78 isolate x
x= 87 solution
2007-06-10 06:18:14 · answer #6 · answered by Anonymous · 0⤊ 0⤋
The four have to average 80
Let x = score on 4th quiz
80 = (83+72+78+x)/4
Cross multiply and combine
320 = 233 + x
x = 87
.
2007-06-10 06:17:12 · answer #7 · answered by Robert L 7 · 0⤊ 0⤋
83+72+78+x=320
233+x=320
233-233+x=320-233
x=87
since 320/4=80
so the least score would be 87
2007-06-10 06:27:39 · answer #8 · answered by saltnsaffron 5 · 0⤊ 0⤋
average score
80 = ( 83 + 72 + 78 + x ) / 4
80 = ( 233 + x ) / 4
320 = 233 + x
x = 87
2007-06-10 06:17:14 · answer #9 · answered by driftaddict87 4 · 0⤊ 0⤋
80x4=320 is the total score for all 4 questions.
so 320-83-72-78= 87 is the necessary score for the 4th question.
2007-06-10 06:20:23 · answer #10 · answered by calvin o 5 · 0⤊ 0⤋