the first two problems demonstrate the first basic variant of the technique-a single bar with two section. This part-whole model works for simple addition and subtraction problems.(Part-whole relationships are a constant theme in Singapore Math ,from 1st graders learning to add to 6th graders learning to divide fractions) For example,
Daniel and Peter have 450 marbles.
Daniel has 248 marbles.
How many marbles does Peter have?