How much water must be added to 100 cc of 80% solution of boric acid to reduce it to a 50% solution ?

A small scale soap business has the following expenses: 10% on marketing, 65% on employees salary and 25% on raw materials. If the business pays a total salary of Rs. 65,000 then what is its marketing expense?

In $2003$, the total population of a village was $4800$, out of which $40\%$ were females. In $2004$, the total population increased by $10\%$ as compared to the previous year. If the number of females remained the same in $2004$, what was the percentage increase in the number of males in $2004$ as compared to $2003$?

There are $1500$ students in a school, $15\%$ are Muslims, $7\%$ are Sikhs, $8\%$ are Christians and remaining are Hindus. How many Hindu students are there in the school?