3 gifts

Chad had 30 dollars to spend on 3 gifts. He spent 9 1/4 dollars on gift A and 3 4/5 dollars on gift B. How much money did he have left for gift C?

Correct answer:

C =  16 ¹⁹⁄₂₀ = 339/20 USD

Step-by-step explanation:

$$\begin{gathered} A=9\frac{1}{4}=9+\frac{1}{4}=\frac{9\cdot 4+1}{4}=\frac{36+1}{4}=\frac{37}{4}=9.25\text{USD} \\ B=3\frac{4}{5}=3+\frac{4}{5}=\frac{3\cdot 5+4}{5}=\frac{15+4}{5}=\frac{19}{5}=3.8\text{USD} \\ A+B+C=30 \\ s=A+B=\frac{37}{4}+\frac{19}{5}=\frac{185}{20}+\frac{76}{20}=\frac{185+76}{20}=\frac{261}{20}=13.05\text{USD} \\ C=30-s=30-\frac{261}{20}=\frac{30\cdot 20}{20}-\frac{261}{20}=\frac{600}{20}-\frac{261}{20}=\frac{600-261}{20}=\frac{339}{20}=\frac{339}{20}\text{USD}=16\frac{19}{20}\text{USD}=16.95\text{USD} \end{gathered}$$

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