Volunteers

Volunteers helped clean up 8.2 kg of trash in one neighborhood and 11 1/2 kg in another. They sent 2 3/5 kg to be recycled and threw the rest away. How many kilograms of trash did they throw away?

Correct answer:

m =  17 ¹⁄₁₀ = 171/10 kg

Step-by-step explanation:

$$\begin{gathered} m_1=8.2\text{kg} \\ {m}_2=11\frac{1}{2}=11+\frac{1}{2}=\frac{11\cdot 2+1}{2}=\frac{22+1}{2}=\frac{23}{2}=11.5\text{kg} \\ r=2\frac{3}{5}=2+\frac{3}{5}=\frac{2\cdot 5+3}{5}=\frac{10+3}{5}=\frac{13}{5}=2.6\text{kg} \\ m=m_1+m_2-r=8.2+11.5-2.6=\frac{171}{10}\text{kg}=17\frac{1}{10}\text{kg}=17.1\text{kg} \end{gathered}$$

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