If the average (arithmetic mean) score for a certain student in Ms Sweeney's class is 74 on his first 6 tests then how many points must that student score on this next test to bring his overall average to 78?

A. 102
B. 84
C. 78
D. 76
E. 74
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Old-fashioned but quick, see diagram below ... A*n=S

1. Find the total current point score total (sum) by multiplying his current average (74, given) by the 6 tests he has taken: 74 * 6 = 444

2. To find what score he needs to boost his overall average, first find needed overall points (second sum):

a. find what would be the overall new number of tests: 6 + 1 = 7

b. take the hoped-for average (78, given), multiply by overall number of tests: 78 * 7 = 546

3. Then, to find the value for the score he needs, simply subtract old total from needed total: 546-444 =
Edited to replace lost text. Why does this interface sometimes eat parts of my posts?
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If the average (arithmetic mean) score for a certain student in Ms Sweeney's class is 74 on his first 6 tests then how many points must that student score on this next test to bring his overall average to 78?

Average of first 6 tests = 74 .
Sum of first 6 test = Average x Number of test = 74 x 6 = 444

Average of 7 tests = 78
Sum of 7 tests = 78 x 7 = 546

Therefore required score in 7th test = 546 - 444 = 102.
Answer A...

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