Question 939949
The mean of a set of n numbers is 12, and the mean of a set of 3n numbers is 6. What is the mean when the two sets are combined? Express your answer as a decimal to the nearest tenth.

Mean is Total/frequency

From the first statement,
Freq = n, Mean is 12, Therefore Total1 = Mean * freq = 12n

From the second statement,
Freq =3n, Mean = 6, Total2 = 18n

Mean of the two sets combined
= (Total1 +Total2) / (freq1+freq2)
= (12n+18n)/(3n+n)
= 30n/4n
= 7.5
( to the nearest tenth)

QED