Minimum requirement
A student needs at least 70 points. She already has 46 and earns 4 points per assignment.46 + 4x ≥ 70 → 4x ≥ 24 → x ≥ 6. She needs at least 6 more assignments.
Model maximums, minimums, capacities, goals, and whole-number decisions with linear inequalities.
20 practical inequality problems with worked solutions and context-based rounding.
After the test
An equation asks for an exact balance. An inequality asks for a range of acceptable values. The key modeling skill is to identify the boundary described by the story and decide whether equality at that boundary is allowed. After solving, the final value must still be interpreted in context — especially when x counts whole people, tickets, boxes, or days.
Story → constraint pipeline
State what x counts or measures, including units.
For example, fixed fee + rate × quantity.
Budget, capacity, minimum score, maximum time, and so on.
Ask whether equality at the boundary is permitted.
Apply units, whole-number rules, and realistic restrictions.
Minimum / maximum dashboard
46 + 4x ≥ 70 → 4x ≥ 24 → x ≥ 6. She needs at least 6 more assignments.
5 + 3x ≤ 32 → 3x ≤ 27 → x ≤ 9. The package can contain at most 9 items.
Whole-number decision rule
Capacity limit
Let x be the number of additional groups:
24 + 8x ≤ 120
8x ≤ 96
x ≤ 12
The room can accept at most 12 complete additional groups.
Rate and time limits
Two-plan inequality
Both sides may contain x because both plans change with the same quantity.
$18 fixed fee plus $3 per use.
$8 fixed fee plus $5 per use.
Boundary and test-value check
For the ticket problem, 14 + 9x ≤ 80 gives a maximum whole-number answer of 7.
Constraint-modeling error log
The boundary value 40 is allowed.
The setup fee occurs once; only the per-item charge repeats.
Rounding upward would violate the upper bound.
Return the bound to the variable definition and units.
Constraint-planner diagnostics