Jika rata rata a dan b 50,b dan c 75,c dan d 70,maka rata rata a dan d adalah

(a + b)/2 = 50
a + b = 100
b = 100 - a

(b + c)/2 = 75
b + c = 150
100 - a + c = 150
c = 150 - 100 + a
c = 50 + a

(c + d)/2 = 70
c + d = 140
50 + a + d = 140
a + d = 140 - 50
a + d = 90
rata2 a + d = (a + d)/2 = 90/2 = 45