The mean of $6$ numbers is $15$. A new number $22$ is added. The mean of the $7$ numbers is:

The mean of $6$ numbers is $15$. A new number $22$ is added. The mean of the $7$ numbers is:
  1. $15$
  2. $16$
  3. $17$
  4. $18$

Solution

Old sum $= 6\times 15 = 90$. New sum $= 90+22 = 112$. New mean $= \dfrac{112}{7} = 16$.

Asked in: IMO

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