Error in operating on a fraction: A boy was asked to find 13/14 of a certain fraction. Instead, he mistakenly divided the fraction by 13/14 and obtained a result that exceeded the correct value by 3/65. What is the correct original fraction?

Difficulty: Medium

Correct Answer: 14/45

Explanation:


Introduction / Context:
This question checks understanding of operations with fractions and how a procedural mistake affects the result. The intended operation was to multiply the unknown fraction by 13/14, but the boy instead divided by 13/14, which is equivalent to multiplying by 14/13. We are told the error increased the answer by 3/65 over the correct value. We must translate this into an equation and solve for the original fraction.


Given Data / Assumptions:

  • The unknown fraction is x.
  • Correct result should be (13/14) * x.
  • Mistaken result is x ÷ (13/14) = (14/13) * x.
  • Excess due to the mistake is 3/65 over the correct result.


Concept / Approach:
Express the stated excess as the difference between the mistaken result and the correct result. This gives a linear equation in x. Solving that equation yields the value of x directly. This is standard equation setup using fraction arithmetic and difference-of-results reasoning.


Step-by-Step Solution:

Correct value = (13/14) * x.Mistaken value = (14/13) * x.Excess = Mistaken − Correct = 3/65.So (14/13)x − (13/14)x = 3/65.Compute the difference: (196/182 − 169/182)x = (27/182)x = 3/65.Solve for x: x = (3/65) * (182/27) = 546/1755 = 14/45 after simplification.


Verification / Alternative check:

Check difference using x = 14/45. Correct: (13/14)*(14/45) = 13/45. Mistaken: (14/13)*(14/45) = 196/(585) = 28/83.75 (same as 196/585). Difference: 196/585 − 13/45 = 196/585 − 169/585 = 27/585 = 3/65. Verified.


Why Other Options Are Wrong:

  • 12/65: Does not satisfy the formed equation; difference is not 3/65.
  • 13/45: This equals the correct result, not the original fraction.
  • 2/7: Produces a different excess; arithmetic check fails.


Common Pitfalls:

  • Confusing multiplying by 13/14 with dividing by 13/14.
  • Not aligning denominators correctly when subtracting the two expressions.


Final Answer:

14/45

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