Benhur

Benhur boiled 1 1/4 liters of water in a kettle. After 10 1/2 minutes he measured the water again. It had 3/4 liters left in the kettle. What is the amount of water that evaporates every minutes?

Correct answer:

w =  1/21 l/min

Step-by-step explanation:

$$\begin{gathered} V_1=1\frac{1}{4}=1+\frac{1}{4}=\frac{1\cdot 4+1}{4}=\frac{5}{4}=1.25\text{l} \\ t=10\frac{1}{2}=10+\frac{1}{2}=\frac{10\cdot 2+1}{2}=\frac{21}{2}=10.5\text{min} \\ {V}_2=3/4=\frac{3}{4}=0.75\text{l} \\ V=V_1-V_2=1.25-0.75=\frac{1}{2}=0.5\text{l} \\ w=V/t=0.5/10.5=\frac{1}{21}\text{l/min}=0.0476\text{l/min} \end{gathered}$$

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