Double number line missing values
Use aligned double number lines to find missing values in proportional situations.
Variation ladder
1Foundation recognitionNotice the relevant quantity, shape, relation, or constraint before calculating.Attention to the relevant objects, relation, or constraint without solving it.
2Guided strategyUse a visible scaffold, model, or narrowing move to choose a valid next step.One scaffolded move, then completion of the decision.
3Core taskSolve the target skill independently.Progressive hints that preserve independent evidence before reveal.
4Transfer formApply the same idea when numbers, wording, or representation changes.The invariant idea and what changed in the representation.
5Challenge extensionCombine the skill with a second idea, hidden constraint, or explanation requirement.Smaller case, counterexample, or explanation before reveal.
6Advanced enrichmentReason about the general method or a non-routine variant.Method hint, not the answer; no copied external source text.
Common slips
Uses the same additive jump where a multiplicative relationship is required.
Reads values from different tick positions as a pair.
Hints and checks
Decision restated without adding a new method.
Common slip nudge: Uses the same additive jump where a multiplicative relationship is required.
One useful scaffold after help is requested.
Use for transfer and bridge variants that combine school fluency with contest-style reasoning.