When 4 is added to the numerator and 10 is subtracted from the denominator of…

2023

When 4 is added to the numerator and 10 is subtracted from the denominator of a fraction, the fraction changes from 8/11 to 3/4. Now, from this changed fraction, if we subtract 4 from the numerator and 10 from the denominator, what is the new fraction?

  1. A.

    178/244

  2. B.

    184/243

  3. C.

    126/256

  4. D.

    168/254

  5. E.

    208/254

Show answer & explanation

Correct answer: B

Concept: When a fraction is given only as a ratio (here 8/11), its actual numerator and denominator are unknown -- treat them as 8k and 11k for some positive whole number k. A further condition that ties the numerator and denominator together (after a stated change, the fraction equals another known ratio) becomes one linear equation in k, solved by cross-multiplication.

Application:

  1. Let the original fraction be 8k/11k, since it must reduce to 8/11 for some whole number k.

  2. Adding 4 to the numerator and subtracting 10 from the denominator changes it to 3/4: (8k + 4)/(11k − 10) = 3/4.

  3. Cross-multiplying: 4(8k + 4) = 3(11k − 10), which simplifies to 32k + 16 = 33k − 30.

  4. Solving gives k = 46, so the original fraction is 368/506, and after the first change it is (368 + 4)/(506 − 10) = 372/496, which equals 3/4.

  5. Now subtract 4 from the numerator and 10 from the denominator of this changed fraction: (372 − 4)/(496 − 10) = 368/486.

  6. Dividing 368/486 by their greatest common factor (2) gives the new fraction, 184/243.

Cross-check: 368/506 divided by 46 gives 8/11, confirming the original ratio, and 372/496 divided by 124 gives 3/4, confirming the stated change. Both given conditions hold, so the new fraction after the second subtraction is 184/243.

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