Definition
Comparison bar model
A comparison bar model lines up two bars so the extra length shows their difference.
What it means
Draw one bar for each quantity. Start both bars at the same place and keep the unit size the same. The longer bar sticks out past the shorter one. That extra part is how much more the larger quantity has—or how much less the smaller quantity has.
Remember it
Same start, same scale; the part that sticks out is the difference.
Example
Mira has 18 stickers and Leo has 11. Draw bars of 18 and 11 units with their left ends aligned. The longer bar has 7 unmatched units, so Mira has 18 − 11 = 7 more stickers.
Watch for
Bars that start in different places or use different unit widths do not show the comparison faithfully. Alignment and scale are part of the mathematics, not decoration.
Common mix-up
This card owns additive difference. A multiplicative comparison asks how many times as many and needs equal-size groups or repeated unit bars, not just the leftover length.
Exact meaning
A comparison bar model represents two quantities with bars that share a starting point and use the same scale. In an additive comparison, the unmatched part of the longer bar represents the difference between the quantities.