The mass of 4 children, Penelope, Jade, Bryan and Howard were taken. Only 3 children can be weighed at one time. Penelope, Jade and Bryan weighed a total of 82 kg. Jade, Bryan and Howard weighed a total of 90 kg. Penelope, Bryan and Howard weighed a total of 132 kg. Penelope, Jade, and Howard weighed a total of 128 kg. What is the average mass of the 4 children?
Penelope + Jade + Bryan = 82 --- (1)
Jade + Bryan + Howard = 90 --- (2)
Penelope + Bryan + Howard = 132 --- (3)
Penelope + Jade + Howard = 128 --- (4)

(1) + (2) + (3) + (4)
3(Penelope + Jade + Bryan + Howard) = 82 + 90 + 132 + 128
3(Penelope + Jade + Bryan + Howard) = 432
Penelope + Jade + Bryan + Howard = 432 ÷ 3 = 144

Total mass of the 4 children = 144

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

Answer(s): 36 kg