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Question
In a series of tests, A appeared for 8 tests. Each test was marked out of 30 and averages 25. However, while checking his files, A could only find 7 of the 8 tests. For these, he scored 29, 26, 18, 20, 27, 24 and 29.
Determine how many marks he scored for the eighth test.
Solution
Total number of tests = 8
The average score of A = 25
Let the score of the 8th test be x.
Then, total score of 8 tests = 29 + 26 + 18 + 20 + 27 + 24 + 29 + x
Now, we have
Mean = `"Total score of 8 tests"/"Total number of tests"`
⇒ 25 = `[ 29 + 26 + 18 + 20 + 27 + 24 + 29 + x ]/8`
⇒ 25 x 8 = 173 + x
⇒ x + 173 = 200
⇒ x = 200 - 173
⇒ x = 27
Thus, A scored 27 marks in the eights test.
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