Four children made the following statements.
Rebecca : The average of Oliver's mass and my mass is 42 kg.
Aria : I am the heaviest.
Oliver : Sebastian is 2 kg lighter than Aria.
Sebastian : Our masses are in consecutive order.

What is the total mass of Rebecca, Aria and Oliver ?
Order of the mass of 4 children:
_____ , Sebastian, _____ , Aria (Heaviest)

Total mass of Rebecca and Oliver 
= 2 x 42
= 84 kg

For Rebecca and Oliver,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Rebecca and Oliver
= 1 u + 1 u + 2
= 2 u + 2

2 u + 2 = 84 
2 u = 84 - 2
2 u = 82

1 u = 82 ÷ 2 = 41

The mass of the four children in consecutive order is 41, 42, 43 and 44.

Total mass of Rebecca, Aria and Oliver
= 41 + 43 + 44
= 128

Answer(s): 128 kg