Success: apply a rise to the correct base then redo a whole-pack choice.
- Retrieve · 2 min. Learners state the original two-large total $54 and three-small total $55.20.
- Model · 4 min. Large pack alone rises 10%:
$27×0.10=$2.70; new pack $29.70; two $59.40. - Guided compare · 5 min. Keep small pack unchanged: three $55.20. Difference $4.20; the previously lower total is now higher. Clearly mark what-if.
- Independent check · 7 min. Learners calculate a separate 8% rise on fictional $50 design fee = $54, and explain why they must not add 8 dollars.
- Challenge · 4 min. Partners test whether 10% off $29.70 returns to $27; it gives $26.73. Discuss base changes; calculate $2.70/$29.70≈9.09% if ready.
- Exit · 3 min. Key: after the 10% large-pack-only rise, three small packs are $4.20 lower for 24 sheets, before unknown delivery.