SOLUTION: After a test, a teacher worked out the average mark for her class of 10 pupils. It was 81% One of the pupils scored only 27%, which was much less than any of the other marks.

Algebra ->  Average -> SOLUTION: After a test, a teacher worked out the average mark for her class of 10 pupils. It was 81% One of the pupils scored only 27%, which was much less than any of the other marks.       Log On


   

Question 93779: After a test, a teacher worked out the average mark for her class of 10 pupils. It was 81%
One of the pupils scored only 27%, which was much less than any of the other marks.
The teacher decided to work out a new average, leaving out the lowest mark. What was the new average?
Found 2 solutions by Nate, jim_thompson5910:
Answer by Nate(3500) About Me  (Show Source):
You can put this solution on YOUR website!
(scores + 27%)/10 = 81%
scores + 27 = 810
scores = 783
~~~
783 / 9 = 87%

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=sum of the scores of the remaining students

First write the percentages in decimal form by dividing by 100:
81 percent=81%2F100=0.81
27 percent=27%2F100=0.27

%280.27%2Bx%29%2F10=0.81 Set up the equation which represents the average (note: the average can be found by adding up everyone's scores and dividing that sum by the number of students who took the test)

0.27%2Bx=8.10 Multiply both sides by 10

x=7.83 Subtract 0.27 from both sides


So the sum of the scores for the remaining 9 students is 7.83. Now divide this sum by 9 to find the new average


7.83%2F9=0.87

Now multiply 0.87 by 100 to get a percentage

0.87%2A100=87

So the new average is 87%