MathChapter 5: Word Problems in Real-Life Situations
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Prompt
Which inequality phrase corresponds to ‘at least’?
💡The boundary is included.
Answer
Greater than or equal to, \(\ge\).
ExampleAt least \(20\) means \(x\ge20\).
Prompt
Which inequality phrase corresponds to ‘at most’?
💡It gives a maximum.
Answer
Less than or equal to, \(\le\).
ExampleAt most \(12\) means \(x\le12\).
Prompt
What does ‘no more than \(a\)’ mean?
💡Exactly \(a\) is allowed.
Answer
The quantity is \(\le a\).
ExampleA load no more than \(50\) kg satisfies \(m\le50\).
Prompt
What does ‘fewer than \(a\)’ mean?
💡The boundary is excluded.
Answer
The quantity is \(<a\).
ExampleFewer than \(30\) items means \(n<30\).
Prompt
What does ‘no less than \(a\)’ mean?
💡It cannot fall below the boundary.
Answer
The quantity is \(\ge a\).
ExampleNo less than \(8\) hours means \(h\ge8\).
Prompt
How is a maximum budget translated?
💡A maximum allows equality.
Answer
The total-cost expression is less than or equal to the budget.
Prompt
How is a minimum revenue target translated?
💡A minimum allows equality.
Answer
The revenue or earnings expression is greater than or equal to the target.
Prompt
When does an inequality sign reverse while solving?
💡Addition and subtraction do not reverse it.
Answer
When both sides are multiplied or divided by a negative number.
ExampleFrom \(-5x\ge20\), obtain \(x\le-4\).
Prompt
How is \(x>416.67\) interpreted for a minimum whole count?
💡Move upward into the solution set.
Answer
The least feasible count is \(417\).
ExampleDo not report \(416\).
Prompt
How is \(x<11.67\) interpreted for a maximum whole count?
💡Move downward into the solution set.
Answer
The greatest feasible count is \(11\).
ExampleRounding to \(12\) violates the inequality.
Prompt
Why is contextual integer selection not ordinary rounding?
💡Nearest is not the goal.
Answer
The chosen integer must satisfy the inequality and requested extreme.
ExampleFor \(n<9.8\), maximum whole \(n\) is \(9\).
Prompt
How do you find when Company B is cheaper than Company A?
💡Preserve the requested direction.
Answer
Write the B expression less than the A expression and solve.
ExampleUse \(B(x)<A(x)\).
Prompt
Is a crossover point included in a strict cheaper-than result?
💡Move beyond equality.
Answer
No. At the crossover the prices are equal, not cheaper.
ExampleIf costs match at \(x=12\), strict savings begin on one side of \(12\).
Prompt
What number-line endpoint represents an inclusive boundary?
💡Equality is allowed.
Answer
A closed endpoint.
Example\(x\ge20\) is closed at \(20\).
Prompt
What number-line endpoint represents a strict boundary?
💡Equality is excluded.
Answer
An open endpoint.
Example\(x<50\) is open at \(50\).
Prompt
What domain restriction commonly follows a contextual inequality?
💡Apply it after solving.
Answer
Counts may need to be nonnegative whole numbers.
ExampleA package count cannot be \(-2\) or \(4.5\).
Prompt
How should a proposed maximum count be checked?
💡Verify boundary behavior.
Answer
Test it in the original inequality and test the next integer to confirm it fails.
ExampleIf \(11\) works but \(12\) exceeds capacity, \(11\) is maximum.
Prompt
What is a common pricing-comparison direction trap?
💡Translate ‘B costs less than A’ literally.
Answer
Writing the requested cheaper company on the greater-than side.
ExampleUse \(B<A\), not \(A<B\).
Prompt
What should a contextual inequality answer include?
💡Return from symbols to context.
Answer
The feasible range or requested extreme, with units and a contextual sentence.
ExampleSay ‘at most \(14\) whole miles,’ not only \(x\le14\).
Prompt
How can a decreasing-resource inequality produce an upper time limit?
💡Track the negative coefficient.
Answer
Its negative rate causes sign reversal when time is isolated.
ExampleFrom \(96-6h\ge30\), obtain \(h\le11\).
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