The mass of 4 children, Sabrina, Olivia, Brandon and Carl were taken. Only 3 children can be weighed at one time. Sabrina, Olivia and Brandon weighed a total of 104 kg. Olivia, Brandon and Carl weighed a total of 104 kg. Sabrina, Brandon and Carl weighed a total of 84 kg. Sabrina, Olivia, and Carl weighed a total of 104 kg. What is the average mass of the 4 children?
Sabrina + Olivia + Brandon = 104 --- (1)
Olivia + Brandon + Carl = 104 --- (2)
Sabrina + Brandon + Carl = 84 --- (3)
Sabrina + Olivia + Carl = 104 --- (4)

(1) + (2) + (3) + (4)
3(Sabrina + Olivia + Brandon + Carl) = 104 + 104 + 84 + 104
3(Sabrina + Olivia + Brandon + Carl) = 396
Sabrina + Olivia + Brandon + Carl = 396 ÷ 3 = 132

Total mass of the 4 children = 132

Average mass of the 4 children
= 132 ÷ 4
= 33

Answer(s): 33 kg