Algebraic Fractions and Rational Expressions
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Algebraic Fractions and Rational Expressions — Free MYP4 Mathematics (Extended) Practice Questions

1QuestionAlgebraic Fraction Word ProblemsConcept Practice
4 marks~6 minCriterion A
A water treatment plant monitors chemical concentration using the rational function

C(t)=2t+4t+1C(t) = \frac{2t + 4}{t + 1}

where CC is the concentration in milligrams per litre and tt is the time in hours after treatment begins. The safe upper limit for the chemical is 2.6 mg/L2.6 \text{ mg/L}.
a
Calculate C(3)C(3), simplifying your answer fully. [2]
b
Advise the plant operator whether the concentration at t=3t = 3 hours requires immediate action, justifying your answer with reference to the safe limit. [2]
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Solutions

2QuestionAdding and Subtracting with Common DenominatorsAssessment Practice
4 marks~6 minCriterion D
A bakery models its average cost per batch of cupcakes (in dollars) using the expression

1200x+800x\frac{1200}{x} + \frac{800}{x}

where 1200 dollars represents ingredient costs, 800 dollars represents labour costs, and xx is the number of batches produced.
a
Simplify 1200x+800x\dfrac{1200}{x} + \dfrac{800}{x} to a single rational expression. [1]
b
The bakery owner uses 2000x\dfrac{2000}{x} to decide how many batches to produce each week. Interpret this expression in the context of the bakery: explain what it reveals about cost behaviour, and advise the owner whether this model alone is sufficient to support production decisions. [3]
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Solutions

3QuestionMultiplying and Dividing Algebraic FractionsAssessment Practice
4 marks~6 minCriterion C
A two-stage water filtration system removes contaminants at each stage. The fraction of contaminants removed by stage one is xx+2\dfrac{x}{x+2} and by stage two is x+2x+4\dfrac{x+2}{x+4}, where x>0x > 0 represents the initial contaminant level. The combined removal fraction is the product of the two stage fractions.
a
Deduce a simplified expression for the combined removal fraction after both stages. [1]
b
The initial contaminant level is x=4x = 4. Calculate the combined removal fraction and interpret what this value means for the filtration system. [2]
c
A filtration engineer claims that this two-stage system is sufficient to meet a safety standard requiring a combined removal fraction greater than 34\dfrac{3}{4} for all x>0x > 0. Justify whether the engineer's claim is correct. [1]
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Solutions

4QuestionAdding and Subtracting with Common DenominatorsAssessment Practice
6 marks~9 minCriterion B
A chemical engineer models the net concentration of a reagent in a reactor using the expression

2x2+3x−5+5x−1x−5−x2+2x−5\frac{2x^2+3}{x-5} + \frac{5x-1}{x-5} - \frac{x^2+2}{x-5}

where xx is temperature in °C and x≠5x \neq 5.
a
Deduce the general rule for adding and subtracting algebraic fractions that share a common denominator QQ. [2]
b
Apply your rule to simplify the expression above, showing all working. [3]
c
The reactor operates safely only when the net concentration expression yields a value greater than 30 for integer temperatures in the range 6≤x≤86 \leq x \leq 8. Justify whether the reactor operates safely across this entire range. [1]

Solutions

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