The mass of 4 children, Vanessa, Risa, Japheth and Jack were taken. Only 3 children can be weighed at one time. Vanessa, Risa and Japheth weighed a total of 100 kg. Risa, Japheth and Jack weighed a total of 46 kg. Vanessa, Japheth and Jack weighed a total of 146 kg. Vanessa, Risa, and Jack weighed a total of 140 kg. What is the average mass of the 4 children?
Vanessa + Risa + Japheth = 100 --- (1)
Risa + Japheth + Jack = 46 --- (2)
Vanessa + Japheth + Jack = 146 --- (3)
Vanessa + Risa + Jack = 140 --- (4)

(1) + (2) + (3) + (4)
3(Vanessa + Risa + Japheth + Jack) = 100 + 46 + 146 + 140
3(Vanessa + Risa + Japheth + Jack) = 432
Vanessa + Risa + Japheth + Jack = 432 ÷ 3 = 144

Total mass of the 4 children = 144

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

Answer(s): 36 kg