Four children made the following statements.
Rachel : The average of Aubrey's mass and my mass is 39 kg.
Noah : I am the heaviest.
Aubrey : Elizabeth is 2 kg lighter than Noah.
Elizabeth : Our masses are in consecutive order.

What is the total mass of Rachel, Noah and Aubrey ?
Order of the mass of 4 children:
_____ , Elizabeth, _____ , Noah (Heaviest)

Total mass of Rachel and Aubrey 
= 2 x 39
= 78 kg

For Rachel and Aubrey,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Rachel and Aubrey
= 1 u + 1 u + 2
= 2 u + 2

2 u + 2 = 78 
2 u = 78 - 2
2 u = 76

1 u = 76 ÷ 2 = 38

The mass of the four children in consecutive order is 38, 39, 40 and 41.

Total mass of Rachel, Noah and Aubrey
= 38 + 40 + 41
= 119

Answer(s): 119 kg