Four children made the following statements.
Lucas : The average of Rael's mass and my mass is 45 kg.
Dylan : I am the heaviest.
Rael : Charlotte is 2 kg lighter than Dylan.
Charlotte : Our masses are in consecutive order.

What is the total mass of Lucas, Dylan and Rael ?
Order of the mass of 4 children:
_____ , Charlotte, _____ , Dylan (Heaviest)

Total mass of Lucas and Rael 
= 2 x 45
= 90 kg

For Lucas and Rael,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Lucas and Rael
= 1 u + 1 u + 2
= 2 u + 2

2 u + 2 = 90 
2 u = 90 - 2
2 u = 88

1 u = 88 ÷ 2 = 44

The mass of the four children in consecutive order is 44, 45, 46 and 47.

Total mass of Lucas, Dylan and Rael
= 44 + 46 + 47
= 137

Answer(s): 137 kg