Four children made the following statements.
Harris : The average of Riordan's mass and my mass is 40 kg.
Ellie : I am the heaviest.
Riordan : Lucy is 2 kg lighter than Ellie.
Lucy : Our masses are in consecutive order.

What is the total mass of Harris, Ellie and Riordan ?
Order of the mass of 4 children:
_____ , Lucy, _____ , Ellie (Heaviest)

Total mass of Harris and Riordan 
= 2 x 40
= 80 kg

For Harris and Riordan,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Harris and Riordan
= 1 u + 1 u + 2
= 2 u + 2

2 u + 2 = 80 
2 u = 80 - 2
2 u = 78

1 u = 78 ÷ 2 = 39

The mass of the four children in consecutive order is 39, 40, 41 and 42.

Total mass of Harris, Ellie and Riordan
= 39 + 41 + 42
= 122

Answer(s): 122 kg