Four children made the following statements.
Isabella : The average of Joshua's mass and my mass is 45 kg.
Lucy : I am the heaviest.
Joshua : Christian is 2 kg lighter than Lucy.
Christian : Our masses are in consecutive order.

What is the total mass of Isabella, Lucy and Joshua ?
Order of the mass of 4 children:
_____ , Christian, _____ , Lucy (Heaviest)

Total mass of Isabella and Joshua 
= 2 x 45
= 90 kg

For Isabella and Joshua,
Mass of the lighter one = 1 u
Mass of the heavier one = 1 u + 2

Total mass of Isabella and Joshua
= 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 Isabella, Lucy and Joshua
= 44 + 46 + 47
= 137

Answer(s): 137 kg