The mass of 4 children, Tammy, Nora, Justin and Glen were taken. Only 3 children can be weighed at one time. Tammy, Nora and Justin weighed a total of 114 kg. Nora, Justin and Glen weighed a total of 126 kg. Tammy, Justin and Glen weighed a total of 141 kg. Tammy, Nora, and Glen weighed a total of 63 kg. What is the average mass of the 4 children?
Tammy + Nora + Justin = 114 --- (1)
Nora + Justin + Glen = 126 --- (2)
Tammy + Justin + Glen = 141 --- (3)
Tammy + Nora + Glen = 63 --- (4)

(1) + (2) + (3) + (4)
3(Tammy + Nora + Justin + Glen) = 114 + 126 + 141 + 63
3(Tammy + Nora + Justin + Glen) = 444
Tammy + Nora + Justin + Glen = 444 ÷ 3 = 148

Total mass of the 4 children = 148

Average mass of the 4 children
= 148 ÷ 4
= 37

Answer(s): 37 kg