Q1 of 69 Page 6

The mean of 11 results is 30. If the mean of the first 6 results is 28 and that of last 6 results is 32, find the 6th result.

Let the 6th number be x


Given that mean of 11 results = 30


∴ sum of 11 numbers = 11 × 30 = 330


Mean of the first 6 results = 28


Sum of first 6 numbers = 6 × 28 = 168


Mean of the last 6 results = 32


Sum of the last 6 results = 6 × 32 = 192


Therefore,


Sum of first 6 numbers + sum of last 6 numbers – 6th number = sum of 11 numbers


168 + 192 - x = 330


⇒ 360 – x = 330


⇒ x = 30


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