Question

. A student scored following marks in five subjects :

90%, 85%, 95%, 70%, 60%
Arithmetic mean of his marks is:


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Answer 1

student's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

(A) 80

(B) 82

(C) 84

(D) 86

(E) 88

Since the student's average test score on 4 tests is 78, then the sum of the first 4 test scores is 4*78=312. We need the sum of ALL 5 scores to be 5*80=400, so if xx is the 5th test score, then 312+x=400312+x=400 --> x=88x=88.

Answer: E. 

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