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28.	The average of 50 numbers is 30. If two numbers, 35 and 40 are discarded, then the average of the remaining numbers is nearly
	A.  28.32
	B.  28.78
	C.  29.27
	D.  29.68

Solution

Sum of 50 numbers = 30 x 50 = 1500. Sum of remaining 48 numbers = 1500 - (35+40) = 1425. ∴ Required average = (1425 / 48) = 475 / 16. = 29.68.

29.	The mean of 50 observations was 36. It was found later that an observation 48 was wrongly taken as 23. The corrected new mean is
	A.  35.2
	B.  36.1
	C.  36.2
	D.  36.5

Solution

Correct sum = (36x50+48-23) = 1825. ∴ Correct mean = 1825 / 50 = 36.5.

30.	The average age of the mother and her six children is 12 years which is reduced by 5 years if the age of the mother is excluded. How old is the mother?
	A.  40 years
	B.  42 years
	C.  50 years
	D.  52 years

Solution

Age of the mother = (12 x 7 - 7 x 6) = 42 years.