2010 AMC 10B Problem 2

Note that $45$ minutes is $$\dfrac{45}{60} = \dfrac{3}{4}$$ hours. The second meeting is then $$2 \cdot \dfrac{3}{4} = \dfrac{3}{2}$$ hours. Both meetings take a total of $$\dfrac{3}{4} + \dfrac{3}{2} = \dfrac{9}{4}$$ hours then. The percent of Makayla’s work day spent attending meetings is $$100 \% \cdot \dfrac{\frac{9}{4}}{9} = 100 \% \cdot \dfrac{1}{4} = 25 \%.$$ Thus, C is the correct answer.