In an exam, $\frac{1}{4}$ of the students failed both in English and Maths, $35\%$ of students failed in Maths and $30\%$ failed in English.

If the number of students who failed only in English was $25$, find the total number of students.

In a sale, a shop reduces all its prices by $15\%$. Calculate the cost of an article which was originally priced at $₹40$. Give the answer in $₹$.

In a sale, a shop reduces all its prices by $15\%$. Calculate the original price of an article which was sold for $₹ 20.40$. Give the answer in $₹$.

Find the profit or loss percentage, when $\mathrm{C}.\mathrm{P}=₹400, \mathrm{S}.\mathrm{P}=₹468$.