Discount sale

At Christmas Sale, after a 20% discount, the cosmetic package was priced at 5 euros and 60 cents; later, it went to 3 euros and 80 cents. How much percentage is the total discount?

Correct answer:

p =  45.7143 %

Step-by-step explanation:

$$\begin{gathered} a-0.20a=5.60 \\ a-0.20\cdot a=5.60 \\ 0.8a=5.6 \\ a=\frac{5.6}{0.8}=7 \\ a=7 \\ b=3.80\text{eur} \\ p=100\cdot \frac{a-b}{a}=100\cdot \frac{7-3.8}{7}=\frac{320}{7}\%=45.7143\% \end{gathered}$$

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