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Linear and Quadratic Equations · Question 42 of 66

Question 42

HardOriginal question

If 2 is added to both the numerator and the denominator of a fraction, it becomes 23\frac{2}{3}. If 3 is subtracted from both, it becomes 12\frac{1}{2}. What is the fraction?

Options for question 42

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. Let the fraction be nd\frac{n}{d}. First condition: 3(n+2)=2(d+2)3(n + 2) = 2(d + 2), so 3n−2d=−23n - 2d = -2.

  2. Second condition: 2(n−3)=d−32(n - 3) = d - 3, so d=2n−3d = 2n - 3.

  3. Substitute: 3n−2(2n−3)=−23n - 2(2n - 3) = -2, so −n+6=−2-n + 6 = -2 and n=8n = 8; then d=13d = 13.

  4. Check: 1015=23\frac{10}{15} = \frac{2}{3} and 510=12\frac{5}{10} = \frac{1}{2}.

Worth noting

1015\frac{10}{15} and 510\frac{5}{10} are the fractions AFTER the changes; 138\frac{13}{8} is the answer turned upside down.

Concept
Fraction problem giving a pair of linear equations
Typical time
120 s
Your time
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The rule this testsWord problems into equations
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Ten questions from Linear and Quadratic Equations, at your own pace.

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Ten questions from Linear and Quadratic Equations, at your own pace.