Question

The mean of a set of eight numbers is 8 and the mean of a different set of twelve numbers is m. Given that the mean if the combined set of twenty numbers is 5, calculate m.

Answer 1

mean=total/the number of values =>total=mean*the number of values
the total of the first set of 8 numbers is : total=8*8=64
the total of the second set of 12 numbers is: 12m
the total of the 20 numbers is: 64+12m
the mean of the 20 number is: (64+12m)/20=5
solve for m: 64+12m=100
12m=36
m=3