Pin Down a Number from Digit and Range Conditions

A hidden number is found by applying clues in turn — digit constraints, place-by-place comparison, and inequality bounds that fence the unknown into a finite range. Early versions narrow a four-digit number from digit clues; later versions bound an unknown digit or an unknown box value under a sum, product, or comparison constraint. The shared move is converting each condition into a restriction until one survivor remains.

grade 2–4 NBTOA Eliminate PossibilitiesMake a Systematic List

Builds on: Place-Value Regrouping

Progression (9)

2-2 1. Compare numbers with an unknown digit 4.NBT.A.2 · foundational

2-2 2. Find a number from digit clues 4.NBT.A.2 · foundational

2-2 3. Bound an inequality at equality 3.OA.A.43.OA.C.7 · foundational

2-2 4. Find a number satisfying product bounds 3.OA.A.43.OA.C.7 · core

3-1 5. Bigger addend, bigger sum 3.OA.A.43.NBT.A.2 · core

3-1 6. Estimate a product to solve an inequality 3.NBT.A.33.OA.D.8 · core

3-2 7. Estimate a product to bound an unknown 3.NBT.A.33.OA.C.7 · advanced

4-1 8. Build a number from digit conditions in order 4.NBT.A.2 · advanced

4-1 9. Compare place by place to bound an unknown digit 4.NBT.A.2 · advanced