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?
- A.
178/244
- B.
184/243
- C.
126/256
- D.
168/254
- 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:
Let the original fraction be 8k/11k, since it must reduce to 8/11 for some whole number k.
Adding 4 to the numerator and subtracting 10 from the denominator changes it to 3/4: (8k + 4)/(11k − 10) = 3/4.
Cross-multiplying: 4(8k + 4) = 3(11k − 10), which simplifies to 32k + 16 = 33k − 30.
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.
Now subtract 4 from the numerator and 10 from the denominator of this changed fraction: (372 − 4)/(496 − 10) = 368/486.
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.