Reduce the fraction $\dfrac{40}{72}$ to lowest terms.
A$\dfrac{8}{14}$
B$\dfrac{5}{9}$
C$\dfrac{2}{3}$
D$\dfrac{20}{36}$
Answer & Solution
Correct answer: B. $\dfrac{5}{9}$
Find the greatest common factor of $40$ and $72$.
$40 = 2^{3} \cdot 5$, $72 = 2^{3} \cdot 3^{2}$. GCF $= 2^{3} = 8$.
Divide both: $\dfrac{40 \div 8}{72 \div 8} = \dfrac{5}{9}$.
- Trap D divides only by $2$.
- Trap C uses a wrong divisor.
- Trap A uses an unrelated reduction.
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