AspectBy necessityBy circumstance
BasisThe necessary remainder implied by speechRole, knowledge, occasion and silence
ExampleMother one-third; father the remainderPre-emption holder remains silent after notice
TestIs the omitted share inevitable?Was a response expected at that time?
Application 1: assigning 40% of a two-party profit division to one party leaves 60% for the other. The explanation is mathematical, not a declaration of consent through silence.
Application 2: an owner sees a person under his authority trading, with a meaningful chance to object. This is a question of an evidentiary circumstance, not the remainder of a fraction.
The fact that both cases involve something unstated should not obscure their different grounds.