The mass of 4 children, Jade, Joelle, Peter and Daniel were taken. Only 3 children can be weighed at one time. Jade, Joelle and Peter weighed a total of 114 kg. Joelle, Peter and Daniel weighed a total of 91 kg. Jade, Peter and Daniel weighed a total of 60 kg. Jade, Joelle, and Daniel weighed a total of 143 kg. What is the average mass of the 4 children?
Jade + Joelle + Peter = 114 --- (1)
Joelle + Peter + Daniel = 91 --- (2)
Jade + Peter + Daniel = 60 --- (3)
Jade + Joelle + Daniel = 143 --- (4)

(1) + (2) + (3) + (4)
3(Jade + Joelle + Peter + Daniel) = 114 + 91 + 60 + 143
3(Jade + Joelle + Peter + Daniel) = 408
Jade + Joelle + Peter + Daniel = 408 ÷ 3 = 136

Total mass of the 4 children = 136

Average mass of the 4 children
= 136 ÷ 4
= 34

Answer(s): 34 kg