Four children made the following statements.
Nora : The average of Samuel's mass and my mass is 30 kg.
Sebastian : I am the heaviest.
Samuel : Grace is 2 kg lighter than Sebastian.
Grace : Our masses are in consecutive order.

What is the total mass of Nora, Sebastian and Samuel ?
Order of the mass of 4 children:
_____ , Grace, _____ , Sebastian (Heaviest)

Total mass of Nora and Samuel 
= 2 x 30
= 60 kg

For Nora and Samuel,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Nora and Samuel
= 1 u + 1 u + 2
= 2 u + 2

2 u + 2 = 60 
2 u = 60 - 2
2 u = 58

1 u = 58 ÷ 2 = 29

The mass of the four children in consecutive order is 29, 30, 31 and 32.

Total mass of Nora, Sebastian and Samuel
= 29 + 31 + 32
= 92

Answer(s): 92 kg