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the mean of n numbers is 5 if the number 13 is now included with n numbers the mean becomes 6 find the value of n
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Let , , , . . . , be the given " n " numbers.
We are given that
= 5. (1)
It means that the sum = is equal to 5n
When the (n+1)-th number = 13 is included with n numbers, the mean of the (n+1) numbers is
= 6.
It implies
= 6(n+1),
Replace here by 5n, based on (1). You will get
5n + 13 = 6(n+1),
5n + 13 = 6n + 6
13 - 6 = 6n - 5n
7 = n.
ANSWER. n = 7.
Solved.
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The setup in the post by @josgarithmetic is INCORRECT;
so, for your safety, you better ignore it.