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Question
The average marks of six students is 8. One more student mark is added and the mean is still 8. Find the student mark that has been added
Solution
Average = `"Sum of all observations"/"Number of observations"`
8 = `"Sum of observation"/8`
Sum of observation = 6 × 8 = 48
If one more mark is added then number of observations = 6 + 1 = 7
Let the number be x
Still average = 8
∴ 8 = `(48 + x)/7`
48 + x = 7 × 8
48 + x = 56
48 + x = 56 – 48
x = 8
∴ The number that is added = 8
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