The mass of 4 children, Penelope, Natalie, Simon and Wesley were taken. Only 3 children can be weighed at one time. Penelope, Natalie and Simon weighed a total of 72 kg. Natalie, Simon and Wesley weighed a total of 101 kg. Penelope, Simon and Wesley weighed a total of 49 kg. Penelope, Natalie, and Wesley weighed a total of 114 kg. What is the average mass of the 4 children?
Penelope + Natalie + Simon = 72 --- (1)
Natalie + Simon + Wesley = 101 --- (2)
Penelope + Simon + Wesley = 49 --- (3)
Penelope + Natalie + Wesley = 114 --- (4)

(1) + (2) + (3) + (4)
3(Penelope + Natalie + Simon + Wesley) = 72 + 101 + 49 + 114
3(Penelope + Natalie + Simon + Wesley) = 336
Penelope + Natalie + Simon + Wesley = 336 ÷ 3 = 112

Total mass of the 4 children = 112

Average mass of the 4 children
= 112 ÷ 4
= 28

Answer(s): 28 kg