The mass of 4 children, Yoko, Marion, Mark and Howard were taken. Only 3 children can be weighed at one time. Yoko, Marion and Mark weighed a total of 49 kg. Marion, Mark and Howard weighed a total of 132 kg. Yoko, Mark and Howard weighed a total of 145 kg. Yoko, Marion, and Howard weighed a total of 106 kg. What is the average mass of the 4 children?
Yoko + Marion + Mark = 49 --- (1)
Marion + Mark + Howard = 132 --- (2)
Yoko + Mark + Howard = 145 --- (3)
Yoko + Marion + Howard = 106 --- (4)

(1) + (2) + (3) + (4)
3(Yoko + Marion + Mark + Howard) = 49 + 132 + 145 + 106
3(Yoko + Marion + Mark + Howard) = 432
Yoko + Marion + Mark + Howard = 432 ÷ 3 = 144

Total mass of the 4 children = 144

Average mass of the 4 children
= 144 ÷ 4
= 36

Answer(s): 36 kg