math
posted by Tricia .
A student has a mean score of 88 on five tests taken. What score must she obtain on her next test to have a mean (average) score of 80 on all six tests?

Mean score of tests :
( x1 + x2 + x3 + x4 + x5 ) / 5 = 88 Multiply both sides by 5
x1 + x2 + x3 + x4 + x5 = 88 * 5
x1 + x2 + x3 + x4 + x5 = 440
Mean score of six tests :
( x1 + x2 + x3 + 4 + x5 + x6 ) / 6 = 80
[ ( x1 + x2 + x3 + 4 + x5 ) + x6 ] / 6 = 80
( 440 + x6 ) / 6 = 80 Multiply both sides by 6
440 + x6 = 80 * 6
440 + x6 =480
x6 = 480  440
x6 = 60 
( x1 + x2 + x3 + x4 + x5 + x6 ) / 6 = 80

x6 = 480  440
x6 = 40
Respond to this Question
Similar Questions

Statistics
Suppose that two different tests A and B are to be given to a student chosen at random from a certain population. Suppose also that the mean score on test A is 85, and the standard deviation is 10; the mean score on test B is 90, and … 
algebra
Jacob has a mean score of 78 after his first four math tests. He wants to make a B, or an average of 80, in math. What does he need to score on the fifth test to have a mean score of 80? 
Math
To get an A in psychology, a student must score an average of 90 on four tests. Scores on the first three tests were 96,92,88. What is the lowest score the student can make on the last test and still get an A? 
math
To get a C in physics, a student must score an average of 70 on four tests. Scores on the first three tests were 63, 85, and 82. What is the lowest score the student can make on the last test and still get a C? 
math
After six biology tests, Ruben has a mean score of 73. What score does Ruben need on the next test to raise his average (mean) to 75? 
social science statistics
a professor was curious to whether the students in a very large class she was teaching who turned in their first scored differently from the overall mean on the test.The overall mean score on the test was 75 with a standard deviation … 
math
Adam took five tests and received a grade for each of them. The first test was 92%, the second test was 83%, and the mean of the five tests was 85%. What can you conclude? 
graduate statistics
A nursing professor was curious as to whether the students in a very large class she was teaching who turned in their tests first scored differently from the overall mean on the test. The overall mean score on the test was 75 with … 
statistics
A student has a mean score of five tests taken. What score must she obtain on her next test to have a mean average of 88 on all six tests? 
bridge
Mr. Feng conducted five math tests. Trinity had completed four tests and scored 79, 78, 82, and 75. She wanted to achieve an average of 80% in her math tests. Write an inequality to find the minimum score Trinity can make on the fifth …