The mass of 4 children, Natalie, Abi, Wesley and Tommy were taken. Only 3 children can be weighed at one time. Natalie, Abi and Wesley weighed a total of 76 kg. Abi, Wesley and Tommy weighed a total of 125 kg. Natalie, Wesley and Tommy weighed a total of 76 kg. Natalie, Abi, and Tommy weighed a total of 59 kg. What is the average mass of the 4 children?
Natalie + Abi + Wesley = 76 --- (1)
Abi + Wesley + Tommy = 125 --- (2)
Natalie + Wesley + Tommy = 76 --- (3)
Natalie + Abi + Tommy = 59 --- (4)

(1) + (2) + (3) + (4)
3(Natalie + Abi + Wesley + Tommy) = 76 + 125 + 76 + 59
3(Natalie + Abi + Wesley + Tommy) = 336
Natalie + Abi + Wesley + Tommy = 336 ÷ 3 = 112

Total mass of the 4 children = 112

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

Answer(s): 28 kg