Question

The mean of three numbers x,y,z us 6 and the mean of five numbers x,y,z,a,b is 8.find the mean of a and b

Answer 1

mean of x, y, z = (x+y+z)/3=6(given)
so, x+y+z=18
mean of x, y, z, a,b=(x+y+z+a+b)/5=8(given)
so, x+y+z+a+b=40
a+b=40-18=22
mean of a and b =11

Answer 2

mean of x, y, z =6 
total numbers = 3 
average  = sum of all observations / no of observations
 6 = sum / 3
6 * 3 = sum
18 = x + y + z
x + y + z+ a + b can be written as 18 + a + b
no of observations = 5
8 = 18 + a + b / 6
6 * 8 = 18 + a + b
48 - 18 = a + b
30 = a + b
no = 2
sum / no = average
30 / 2 = avg
15 = average