Definition
Part–whole relationship
A part–whole relationship shows how parts combine to make one complete whole.
What it means
Start with the whole, then split or describe it in parts. Every part must belong to the same whole, and each piece is counted once. Put all the parts back together and you recover the whole. The parts do not have to be equal unless the problem says they are.
Remember it
All the parts, once each, make the whole.
Example
A box holds 7 red pencils and 5 blue pencils. The colour groups are the parts. Together they make the whole box: 7 + 5 = 12 pencils.
Watch for
The parts must describe the same kind of whole and use compatible units. Seven pencils and five centimetres cannot be combined as parts of one quantity.
Common mix-up
Parts need not be equal. Equal parts matter for names such as halves or thirds, not for every part–whole relationship.
Exact meaning
A part–whole relationship describes one whole as non-overlapping parts that, taken together, account for all of that whole.