Four children made the following statements.
Stella : David is 2 kg heavier than Audrey.
Audrey : Our masses are in consecutive order.
Emma : The average of Stella's mass and my mass is 39 kg.
David : I am the heaviest.

What is the total mass of Emma, David and Stella ?
Order of the mass of 4 children:
_____ , Audrey, _____ , David (Heaviest)

Total mass of Emma and Stella
= 2 x 39
= 78 kg

For Emma and Stella,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Emma and Stella
= 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 Emma, David and Stella
= 38 + 40 + 41
= 119

Answer(s): 119 kg