Which of the following is not in the lowest form?
\(\tfrac{7}{5}\)
\(\tfrac{15}{20}\)
\(\tfrac{13}{33}\)
\(\tfrac{27}{28}\)
Meaning of “lowest form”
A fraction is in lowest form when the numerator and denominator have no common factor other than 1.
Check option A
( frac{7}{5})
Factors of 7: 1, 7.
Factors of 5: 1, 5.
Common factor: 1 only → already in lowest form.
Check option B
( frac{15}{20})
Common factor: 5.
Divide both by 5:
(15 div 5 = 3), (20 div 5 = 4).
So ( frac{15}{20} = frac{3}{4}) → not in lowest form.
Check option C
( frac{13}{33})
13 is prime and does not divide 33 → common factor 1 → lowest form.
Check option D
( frac{27}{28})
Prime factors of 27: 3 × 3 × 3.
Prime factors of 28: 2 × 2 × 7.
No common factor → lowest form.
Conclusion
Only ( frac{15}{20}) is not in the lowest form. Answer: Option B.