Question

The mean of 17 observations is 20. If mean of first nine observations is 23 and that of last nine observations is 18. Find the 9th observation.​

Answer 1

Answer: 27

Step-by-step explanation:

9th observation = Sum of first 9 observations + sum of last 9 observations-sum of 17 observations

Let 9th observation be 'x'.

Sum of first 9 observations = 9x23 = 207

Sum of last 9 observations = 9x18 = 162

Sum of 17 observations = 340

Hence, x= 207+162 - 340

x=29