Arelli

Arelli had 20 minutes to do a three-problem quiz. She spent 9 7/10 minutes on question A and 3 2/5 minutes on question B. How much time did she have left for question C?
Solve on paper to find the answer as a fraction.

Correct answer:

c =  6 ⁹⁄₁₀ = 69/10 min

Step-by-step explanation:

$$\begin{gathered} t=20\text{min} \\ a=9\frac{7}{10}=9+\frac{7}{10}=\frac{9\cdot 10+7}{10}=\frac{90+7}{10}=\frac{97}{10}=9.7\text{min} \\ b=3\frac{2}{5}=3+\frac{2}{5}=\frac{3\cdot 5+2}{5}=\frac{15+2}{5}=\frac{17}{5}=3.4\text{min} \\ c=t-a-b=20-\frac{97}{10}-\frac{17}{5}=\frac{69}{10}\text{min}=6\frac{9}{10}\text{min}=6.9\text{min} \end{gathered}$$

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