# NCERT Mathematics Class 9 Exemplar Ch 14 Statistics and Probability Part 3

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12. If the mean of the observations: , , , , is 9, the mean of the last three observations is

(A)

(B)

(C)

(D)

Answer: C

13. If x represents the mean of n observations then value of is:

(A)

(B)

(C)

(D)

Answer: B

14. If each observation of the data is increased by 5, then their mean

(A) Remains the same

(B) Becomes 5 times the original mean

(C) Is decreased by 5

(D) Is increased by 5

Answer: D

15. Let x be the mean of and the mean of. If is the mean of, then is equal to

(A)

(B)

(C)

(D)

Answer: B

16. If is the mean of , then for, the mean of , is

(A)

(B)

(C) (

(D)

Answer: B

17. If are the means of n groups with number of observations respectively, then the mean x of all the groups taken together is given by :

(A)

(B)

(C)

(D)

Answer: C

18. The mean of 100 observations is 50. If one of the observations which were 50 is replaced by 150, the resulting mean will be:

(A)

(B)

(C)

(D)

Answer: B