Butter

The same amount of butter is cut evenly from a cuboid every day. In seven days we used so much butter that all its dimensions were halved.

a) How much percent of butter do we still have left?

b) How many days will the butter last if we continue to cut the same amount every day?

Correct answer:

p =  12.5 %
d =  1 d

Step-by-step explanation:

$$\begin{gathered} V_1=abc \\ {V}_2=\frac{a}{2}\cdot \frac{b}{2}\cdot \frac{c}{2}=\frac{abc}{8}=\frac{V_1}{8} \\ p=100\cdot \frac{V_2}{V_1} \\ p=100\cdot \frac{1}{8}=\frac{100\cdot 1}{8}=\frac{100}{8}=\frac{25}{2}\%=12.5\% \end{gathered}$$

$$\begin{gathered} 7d\dots .7/8 \\ d=1=1\text{d} \end{gathered}$$

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